original discussion in microsoft/vscode#96779

Up to now in LSP v3.15, textEdit/additionalTextEdits are calculated in textDocument/completion, and are not allowed to change during comepltionItem/resolve. This leads to a performance issue of Java language server, because it takes time to calculate additionalTextEdits like "import" statements.

Now in vscode, it offers a pragmatic solution, that additionalTextEdits can be calculated during comepltionItem/resolve, as mentioned in microsoft/vscode#96779 (comment) . Then come the problem, how does the language server know if the client supports the "pragmatic solution", i.e., lazy-loading addtionalTextEdits. So I think a corresponding client capability should be introduced for it.