Convert INDEX_NAME to a configurable parameter

This allows benchmarking multiple setups with separated indices.
The index name can be changed via the settings endpoint.

Also added an option to change from the frontend - but can be removed if this is not something that should be exposed to the user.

Detailed changes (AI-generated):

Backend Changes:

1. config_manager.py: Added index_name: str = "documents" field to KnowledgeConfig dataclass

2. config/settings.py: Removed INDEX_NAME constant and added get_index_name() function to retrieve from config

3. Updated all files using INDEX_NAME: Replaced constant with get_index_name() function call in:

   • main.py (index initialization)
   • services/search_service.py
   • services/document_service.py
   • models/processors.py
   • api/documents.py
   • api/v1/documents.py
   • utils/embedding_fields.py

4. api/settings.py:

   • Added index_name to GET response
   • Added validation (non-empty string)
   • Added update logic with telemetry tracking
   • Integrated with Langflow to update ingest/chat flows when index name changes

5. services/flows_service.py: Added update_flows_index_name() method to update the OpenSearch components in Langflow

6. utils/telemetry/message_id.py: Added ORB_SETTINGS_INDEX_NAME_UPDATED telemetry event

Frontend Changes:

1. useGetSettingsQuery.ts: Added index_name?: string to KnowledgeSettings interface
2. useUpdateSettingsMutation.ts: Added index_name?: string to UpdateSettingsRequest interface
3. settings/page.tsx:
   • Added state management for indexName
   • Added handleIndexNameChange() handler with debounced updates
   • Added UI input field in the Knowledge section (between embedding model and chunk size fields)

Summary:

The index name can now be:

• Configured in config.yaml under knowledge.index_name
• Retrieved via GET /api/settings
• Updated via POST /api/settings with automatic Langflow flow synchronization
• Edited through the Settings page UI with auto-save functionality