[Enhancement] Add support for Chat Template params

[psriramsnc]

🚀 Add support for Chat Template params

✨ Summary

This PR adds support for chat_template_params in model configurations and updates the documentation accordingly.
The purpose is to enable dynamic parameter injection into chat templates, allowing more flexible control over model behavior (e.g., reasoning effort).

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🛠️ Explain the features implemented:

• ➕ Added chat_template_params field in model_configuration.md under Configuration Properties.
• 🔄 Updated all model generation methods in custom_models.py to pass chat_template_params dynamically during request payload creation.
• 📝 Extended get_chat_formatted_text() to accept and apply **chat_template_params.
• 📚 Enhanced documentation to indicate that both parameters and chat_template_params can be overridden in graph YAML files.

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⚡ Performance impact (if any):

• Negligible.
• No measurable performance degradation; parameters are applied only when specified.

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🧪 How to Test the feature

Steps for reviewers to verify functionality:

1. 📂 Navigate to your model configuration YAML file.
2. ✍️ Add custom valid model chat template parameters under chat_template_params, for example:

   gpt-oss-120b:
     completions_api: true
     chat_template_params:
       reasoning_effort: high

3. ✍️ Add chat_template_params in graph_config.yaml to override model configuration YAML file. for example:

   model:
     name: gpt-oss-120b
     chat_template_params:
       reasoning_effort: low

4.▶️ Run a graph YAML that uses this model.
5. 👀 Observe that the model request payloads include the provided chat template parameters and modify output behavior accordingly.

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📸 Screenshots (if applicable)

N/A — documentation-only visual updates and backend enhancements.

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✅ Checklist

• Lint fixes and unit testing done
• End to end task testing
• Documentation updated

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📝 Notes

This change improves extensibility for models using complex prompt templates.

Backward-compatible — existing configurations remain valid without modification.

[zephyrzilla]

LGTM 🚀

[amitsnow]

LGTM