[FEATURE] Allow `LlmGenerationClient::geneate()` directly return a JSON value

[badmonster0]

We may change the trait to allow LlmGenerationClient::geneate() directly return a JSON. The return type can be an enum, with either a JSON or a String, depending on if JSON schema is provided in request.

Originally posted by @badmonster0 in #395 (comment)

[par4m]

I can work on this, please assign!

[badmonster0]

hi @par4m thanks a lot for taking a look at this ticket, we freed up this ticket for now since it has been inactive for a month, if you are actively working on it, please let us know and we will reassign to you!
really appreciate your contribution!

[aryasoni98]

I’m happy to work on this! Could you please assign the issue to me?

[georgeh0]

I’m happy to work on this! Could you please assign the issue to me?

@aryasoni98 thanks for requesting. I already assigned #994 to you as requested. We encourage contributors taking one issue at a time especially at the beginning. We'll assign more issues after the existing one is done. Thanks!