feat: model registry and capabilities for multi-provider support (#2158)

* feat: Implement model registry and capabilities for multi-provider support

- Added ModelRegistry to manage available models and their capabilities.
- Introduced ModelProvider enum for different LLM providers.
- Created ModelCapabilities dataclass to define model features.
- Implemented methods to load models based on API keys and settings.
- Added utility functions for model management in model_utils.py.
- Updated settings.py to include provider-specific API keys.
- Refactored LLM classes (Anthropic, OpenAI, Google, etc.) to utilize new model registry.
- Enhanced utility functions to handle token limits and model validation.
- Improved code structure and logging for better maintainability.

* feat: Add model selection feature with API integration and UI component

* feat: Add model selection and default model functionality in agent management

* test: Update assertions and formatting in stream processing tests

* refactor(llm): Standardize model identifier to model_id

* fix tests

---------

Co-authored-by: Alex <a@tushynski.me>

application/api/answer/routes/answer.py

@@ -54,6 +54,10 @@ class AnswerResource(Resource, BaseAnswerResource):
                 default=True,
                 description="Whether to save the conversation",
             ),
+            "model_id": fields.String(
+                required=False,
+                description="Model ID to use for this request",
+            ),
             "passthrough": fields.Raw(
                 required=False,
                 description="Dynamic parameters to inject into prompt template",
@@ -97,6 +101,7 @@ class AnswerResource(Resource, BaseAnswerResource):
                 isNoneDoc=data.get("isNoneDoc"),
                 index=None,
                 should_save_conversation=data.get("save_conversation", True),
+                model_id=processor.model_id,
             )
             stream_result = self.process_response_stream(stream)