[5h] Prepare general endpoint for operating with RAG agent

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The issue title mentions a RAG agent endpoint but provides no details. Start by examining the existing API structure in the Django REST Framework project, looking for related agent or AI service code. Determine what 'operating with RAG agent' entails—likely creating, querying, or managing a Retrieval-Augmented Generation system. Check for similar endpoints or agent integrations to understand the required request/response format and dependencies.

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