…VIDIA#157)

Closes: NVIDIA#156

This PR adds support for environment variable interpolation in YAML configuration files using the format `${VAR:-default_value}`. This allows developers to:

1. Reference environment variables in configuration
2. Provide default values if the environment variable is not set
3. Use empty strings as default values if needed

To illustrate this concept, an example from the `llms` section of the configuration file is provided below.

```yaml
llms:
  nim_llm:
    _type: nim
    base_url: ${NIM_BASE_URL:-"http://default.com"}  # Optional with default value
    api_key: ${NIM_API_KEY}  # Will use empty string if `NIM_API_KEY` not set
    model_name: ${MODEL_NAME:-}  # Will use empty string if `MODEL_NAME` not set
    temperature: 0.0
```

The environment variable interpolation process follow the rules enumerated below.

- `${VAR}` - Uses the value of environment variable `VAR`, or empty string if not set
- `${VAR:-default}` - Uses the value of environment variable `VAR`, or `default` if not set
- `${VAR:-}` - Uses the value of environment variable `VAR`, or empty string if not set

## By Submitting this PR I confirm:
- I am familiar with the [Contributing Guidelines](https://github.com/NVIDIA/AgentIQ/blob/develop/docs/source/advanced/contributing.md).
- We require that all contributors "sign-off" on their commits. This certifies that the contribution is your original work, or you have rights to submit it under the same license, or a compatible license.
  - Any contribution which contains commits that are not Signed-Off will not be accepted.
- When the PR is ready for review, new or existing tests cover these changes.
- When the PR is ready for review, the documentation is up to date with these changes.

Authors:
  - Matthew Penn (https://github.com/mpenn)
  - David Gardner (https://github.com/dagardner-nv)
  - Yuchen Zhang (https://github.com/yczhang-nv)

Approvers:
  - Michael Demoret (https://github.com/mdemoret-nv)

URL: NVIDIA#157
Signed-off-by: Yuchen Zhang <134643420+yczhang-nv@users.noreply.github.com>

…VIDIA#157)

Closes: NVIDIA#156

This PR adds support for environment variable interpolation in YAML configuration files using the format `${VAR:-default_value}`. This allows developers to:

1. Reference environment variables in configuration
2. Provide default values if the environment variable is not set
3. Use empty strings as default values if needed

To illustrate this concept, an example from the `llms` section of the configuration file is provided below.

```yaml
llms:
  nim_llm:
    _type: nim
    base_url: ${NIM_BASE_URL:-"http://default.com"}  # Optional with default value
    api_key: ${NIM_API_KEY}  # Will use empty string if `NIM_API_KEY` not set
    model_name: ${MODEL_NAME:-}  # Will use empty string if `MODEL_NAME` not set
    temperature: 0.0
```

The environment variable interpolation process follow the rules enumerated below.

- `${VAR}` - Uses the value of environment variable `VAR`, or empty string if not set
- `${VAR:-default}` - Uses the value of environment variable `VAR`, or `default` if not set
- `${VAR:-}` - Uses the value of environment variable `VAR`, or empty string if not set

## By Submitting this PR I confirm:
- I am familiar with the [Contributing Guidelines](https://github.com/NVIDIA/AgentIQ/blob/develop/docs/source/advanced/contributing.md).
- We require that all contributors "sign-off" on their commits. This certifies that the contribution is your original work, or you have rights to submit it under the same license, or a compatible license.
  - Any contribution which contains commits that are not Signed-Off will not be accepted.
- When the PR is ready for review, new or existing tests cover these changes.
- When the PR is ready for review, the documentation is up to date with these changes.

Authors:
  - Matthew Penn (https://github.com/mpenn)
  - David Gardner (https://github.com/dagardner-nv)
  - Yuchen Zhang (https://github.com/yczhang-nv)

Approvers:
  - Michael Demoret (https://github.com/mdemoret-nv)

URL: NVIDIA#157
Signed-off-by: Eric Evans <194135482+ericevans-nv@users.noreply.github.com>

…VIDIA#157)

Closes: NVIDIA#156

This PR adds support for environment variable interpolation in YAML configuration files using the format `${VAR:-default_value}`. This allows developers to:

1. Reference environment variables in configuration
2. Provide default values if the environment variable is not set
3. Use empty strings as default values if needed

To illustrate this concept, an example from the `llms` section of the configuration file is provided below.

```yaml
llms:
  nim_llm:
    _type: nim
    base_url: ${NIM_BASE_URL:-"http://default.com"}  # Optional with default value
    api_key: ${NIM_API_KEY}  # Will use empty string if `NIM_API_KEY` not set
    model_name: ${MODEL_NAME:-}  # Will use empty string if `MODEL_NAME` not set
    temperature: 0.0
```

The environment variable interpolation process follow the rules enumerated below.

- `${VAR}` - Uses the value of environment variable `VAR`, or empty string if not set
- `${VAR:-default}` - Uses the value of environment variable `VAR`, or `default` if not set
- `${VAR:-}` - Uses the value of environment variable `VAR`, or empty string if not set

## By Submitting this PR I confirm:
- I am familiar with the [Contributing Guidelines](https://github.com/NVIDIA/AgentIQ/blob/develop/docs/source/advanced/contributing.md).
- We require that all contributors "sign-off" on their commits. This certifies that the contribution is your original work, or you have rights to submit it under the same license, or a compatible license.
  - Any contribution which contains commits that are not Signed-Off will not be accepted.
- When the PR is ready for review, new or existing tests cover these changes.
- When the PR is ready for review, the documentation is up to date with these changes.

Authors:
  - Matthew Penn (https://github.com/mpenn)
  - David Gardner (https://github.com/dagardner-nv)
  - Yuchen Zhang (https://github.com/yczhang-nv)

Approvers:
  - Michael Demoret (https://github.com/mdemoret-nv)

URL: NVIDIA#157
Signed-off-by: Eric Evans <194135482+ericevans-nv@users.noreply.github.com>

…VIDIA#157)

Closes: NVIDIA#156

This PR adds support for environment variable interpolation in YAML configuration files using the format `${VAR:-default_value}`. This allows developers to:

1. Reference environment variables in configuration
2. Provide default values if the environment variable is not set
3. Use empty strings as default values if needed

To illustrate this concept, an example from the `llms` section of the configuration file is provided below.

```yaml
llms:
  nim_llm:
    _type: nim
    base_url: ${NIM_BASE_URL:-"http://default.com"}  # Optional with default value
    api_key: ${NIM_API_KEY}  # Will use empty string if `NIM_API_KEY` not set
    model_name: ${MODEL_NAME:-}  # Will use empty string if `MODEL_NAME` not set
    temperature: 0.0
```

The environment variable interpolation process follow the rules enumerated below.

- `${VAR}` - Uses the value of environment variable `VAR`, or empty string if not set
- `${VAR:-default}` - Uses the value of environment variable `VAR`, or `default` if not set
- `${VAR:-}` - Uses the value of environment variable `VAR`, or empty string if not set

## By Submitting this PR I confirm:
- I am familiar with the [Contributing Guidelines](https://github.com/NVIDIA/AgentIQ/blob/develop/docs/source/advanced/contributing.md).
- We require that all contributors "sign-off" on their commits. This certifies that the contribution is your original work, or you have rights to submit it under the same license, or a compatible license.
  - Any contribution which contains commits that are not Signed-Off will not be accepted.
- When the PR is ready for review, new or existing tests cover these changes.
- When the PR is ready for review, the documentation is up to date with these changes.

Authors:
  - Matthew Penn (https://github.com/mpenn)
  - David Gardner (https://github.com/dagardner-nv)
  - Yuchen Zhang (https://github.com/yczhang-nv)

Approvers:
  - Michael Demoret (https://github.com/mdemoret-nv)

URL: NVIDIA#157

…VIDIA#157)

Closes: NVIDIA#156

This PR adds support for environment variable interpolation in YAML configuration files using the format `${VAR:-default_value}`. This allows developers to:

1. Reference environment variables in configuration
2. Provide default values if the environment variable is not set
3. Use empty strings as default values if needed

To illustrate this concept, an example from the `llms` section of the configuration file is provided below.

```yaml
llms:
  nim_llm:
    _type: nim
    base_url: ${NIM_BASE_URL:-"http://default.com"}  # Optional with default value
    api_key: ${NIM_API_KEY}  # Will use empty string if `NIM_API_KEY` not set
    model_name: ${MODEL_NAME:-}  # Will use empty string if `MODEL_NAME` not set
    temperature: 0.0
```

The environment variable interpolation process follow the rules enumerated below.

- `${VAR}` - Uses the value of environment variable `VAR`, or empty string if not set
- `${VAR:-default}` - Uses the value of environment variable `VAR`, or `default` if not set
- `${VAR:-}` - Uses the value of environment variable `VAR`, or empty string if not set

## By Submitting this PR I confirm:
- I am familiar with the [Contributing Guidelines](https://github.com/NVIDIA/AgentIQ/blob/develop/docs/source/advanced/contributing.md).
- We require that all contributors "sign-off" on their commits. This certifies that the contribution is your original work, or you have rights to submit it under the same license, or a compatible license.
  - Any contribution which contains commits that are not Signed-Off will not be accepted.
- When the PR is ready for review, new or existing tests cover these changes.
- When the PR is ready for review, the documentation is up to date with these changes.

Authors:
  - Matthew Penn (https://github.com/mpenn)
  - David Gardner (https://github.com/dagardner-nv)
  - Yuchen Zhang (https://github.com/yczhang-nv)

Approvers:
  - Michael Demoret (https://github.com/mdemoret-nv)

URL: NVIDIA#157