LiteLLM API key Config

[memsranga]

Description

Adds support to provide api_key directly to config instead of setting in env variables. Since the model defaults to gpt-4o-mini, key also defaults to OPENAI_API_KEY if not provided.

Fixes #1746

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (does not change functionality, e.g. code style improvements, linting)
• Documentation update

How Has This Been Tested?

Tested by giving api_key directly to config instead of env variables

Please delete options that are not relevant.

• Unit Test
• Test Script (please provide)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

Maintainer Checklist

• closes Add support for API key configuration in LiteLLM #1746
• Made sure Checks passed

[CLAassistant]

All committers have signed the CLA.

[memsranga]

Ignore, the other PR #1747 solves it already.