Add examples and json_schema_extra to @computed_field

[alexmojaki]

Change Summary

• Adds two parameters to computed_field with the same meanings as in Field to add info to the JSON schema. examples solves the primary user request, json_schema_extra was also mentioned in the issue comments.
• Updated some stale arg descriptions in the computed_field docstring,
• Factored out common code for handling json_schema_extra in GenerateSchema.

Related issue number

Closes #7864

Checklist

• The pull request title is a good summary of the changes - it will be used in the changelog
• Unit tests for the changes exist
• Tests pass on CI
• Documentation reflects the changes where applicable
• My PR is ready to review, please add a comment including the phrase "please review" to assign reviewers

Selected Reviewer: @Kludex

[alexmojaki]

I moved this so that the overload and the actual signature matched better so they were easier to compare. Then I noticed that here it's repr: bool = True but the actual signature has repr: bool | None = None, is that intentional?

[sydney-runkle]

Good question.

I don't think so. I think we should use repr: bool | None = None here as well. As far as I understand it, the reason we allow None here is so that we can enforce a default of True if the computed_field is public and False if it's not.

[alexmojaki]

please review

[sydney-runkle]

LGTM otherwise. Thanks for factoring out the common logic re the get_json_schema_update_func and add_json_schema_extra. Definitely cleaner now.

[sydney-runkle]

Good question.

I don't think so. I think we should use repr: bool | None = None here as well. As far as I understand it, the reason we allow None here is so that we can enforce a default of True if the computed_field is public and False if it's not.

[sydney-runkle]

@alexmojaki,

I'm going to go ahead and merge this, thanks for your work on it. I opened an issue to add some better docs and type hints, as we've discussed in this PR.