add finetuning hyperparams

[janukobytsch]

Adds learning_rate_multiplier and batch_size parameters.

Supported by both OpenAI and Azure, see:

• https://platform.openai.com/docs/api-reference/fine-tuning/create
• https://learn.microsoft.com/en-us/rest/api/azureopenai/fine-tuning/create?view=rest-azureopenai-2024-03-01-preview&tabs=HTTP#finetuninghyperparameters

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.88%. Comparing base (774fc9d) to head (e9132c6).
Report is 27 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #793      +/-   ##
==========================================
+ Coverage   98.46%   98.88%   +0.42%     
==========================================
  Files          24       26       +2     
  Lines        1364     1343      -21     
==========================================
- Hits         1343     1328      -15     
+ Misses         15        9       -6     
  Partials        6        6              

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[sashabaranov]

Thank you!