Make reponse format JSONSchema optional

[tylergannon]

Describe the change
This morning's PR #813 makes it impossible to do ChatCompletionRequest that doesn't supply a json schema.

Describe your solution
I followed the suggestion in #818, changing the JSONSchema attached to a request format object to a pointer type, so that the JSON marshaler can properly exclude it when not provided.

Tests
I ran the go tests. (did you guys know you have a bunch of broken tests in the repo?)
All tests pass except for the ones in the jsonschema directory. Those tests were broken both before and after my changes.

I updated my own software to use my fork, and everything works.

Issue: #818

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.88%. Comparing base (774fc9d) to head (7d18593).
Report is 36 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #820      +/-   ##
==========================================
+ Coverage   98.46%   98.88%   +0.42%     
==========================================
  Files          24       26       +2     
  Lines        1364     1347      -17     
==========================================
- Hits         1343     1332      -11     
+ Misses         15        9       -6     
  Partials        6        6              

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[sashabaranov]

Thank you for the PR! I wonder why our integration tests did not catch that

[sashabaranov]

@tylergannon oh also it broke tests https://github.com/sashabaranov/go-openai/actions/runs/10290697434/job/28481256130

[gspeicher]

Thank you for the PR! I wonder why our integration tests did not catch that

@sashabaranov there doesn't appear to be an integration test with a ResponseFormat that uses ChatCompletionResponseFormatTypeJSONObject, which would have caught the oversight.

[tylergannon]

Glad it was such an easy fix.

[eiixy]

I'm very sorry, the integration tests did not cover this part of the functionality.

[HaraldNordgren]

@sashabaranov The integration tests are failing now. Is it safe to use this latest version?

[HaraldNordgren]

@sashabaranov @tylergannon @eiixy Follow-up to make sure the integration tests run for a PR (most are skipped), but it still verifies the overall syntax I believe:

#823

I use this API for production, so it's important to me that it works well 🚀