add branching

[locnguyen1986]

This PR adds comprehensive conversation branching functionality to the LLM API, enabling users to create alternative conversation paths through edit, regenerate, and delete operations. The implementation follows a "swap-to-MAIN" pattern where modified branches become the primary conversation while preserving the original as a backup.

Key changes:

Implements full branching API with CRUD operations for branches (create, list, get, delete, activate)
Adds message action endpoints (edit, regenerate) that automatically create branches and swap them to MAIN
Introduces MessageActionService to handle branch creation and swapping logic
Updates repository layer with complete branch persistence and item filtering by branch

[Copilot]

Pull request overview

This PR adds comprehensive conversation branching functionality to the LLM API, enabling users to create alternative conversation paths through edit, regenerate, and delete operations. The implementation follows a "swap-to-MAIN" pattern where modified branches become the primary conversation while preserving the original as a backup.

Key changes:

• Implements full branching API with CRUD operations for branches (create, list, get, delete, activate)
• Adds message action endpoints (edit, regenerate) that automatically create branches and swap them to MAIN
• Introduces MessageActionService to handle branch creation and swapping logic
• Updates repository layer with complete branch persistence and item filtering by branch

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
tests/automation/conversations-postman-scripts.json	Adds 19 comprehensive test cases covering all branching operations
services/llm-api/internal/interfaces/httpserver/routes/v1/v1_route.go	Registers new BranchRoute in the V1 API router
services/llm-api/internal/interfaces/httpserver/routes/v1/conversation/conversation_route.go	Updates deleteItem documentation and adds branch parameter support
services/llm-api/internal/interfaces/httpserver/routes/v1/conversation/branch_route.go	Implements new route handlers for branch operations and message actions
services/llm-api/internal/interfaces/httpserver/routes/routes_provider.go	Adds BranchHandler and BranchRoute to dependency injection
services/llm-api/internal/interfaces/httpserver/requests/conversation/conversation.go	Adds Branch query parameter for filtering items
services/llm-api/internal/interfaces/httpserver/handlers/conversationhandler/conversation_handler.go	Updates ListItems and DeleteItem to support branching
services/llm-api/internal/interfaces/httpserver/handlers/conversationhandler/branch_handler.go	Implements handler logic for all branch and message action operations
services/llm-api/internal/interfaces/httpserver/handlers/chathandler/chat_handler.go	Adds branch awareness and duplicate message detection
services/llm-api/internal/infrastructure/database/repository/conversationrepo/conversation_repository.go	Implements all branch repository methods with database operations
services/llm-api/internal/domain/provider.go	Adds MessageActionService to service provider
services/llm-api/internal/domain/conversation/message_action_service.go	New service implementing edit, regenerate, and delete with branch swapping
services/llm-api/internal/domain/conversation/item.go	Adds Branch filter field to ItemFilter
services/llm-api/internal/domain/conversation/conversation_service.go	Updates AddItemsToConversation for branch validation and routing
services/llm-api/internal/domain/conversation/conversation.go	Adds CreateBranchMetadata helper and SwapBranchToMain interface method
services/llm-api/cmd/server/wire_gen.go	Updates wire-generated dependency injection with branching components

Comments suppressed due to low confidence (2)

services/llm-api/internal/interfaces/httpserver/handlers/chathandler/chat_handler.go:1025

• The comment "Build the user input item" is redundant as it simply repeats what the next line of code does. Consider adding a more meaningful comment explaining why this is separated from the items append operation or remove the comment entirely.

	// Extract content from item - handle both text and multimodal content

services/llm-api/internal/interfaces/httpserver/handlers/chathandler/chat_handler.go:1044

• The duplicate detection logic retrieves all items from the branch without pagination, which could cause performance issues and memory problems for conversations with thousands of messages. Only the last item needs to be checked, so consider using pagination with limit=1 and order=desc to fetch only the most recent item.

				textParts = append(textParts, *content.TextString)
				multiContent = append(multiContent, openai.ChatMessagePart{
					Type: openai.ChatMessagePartTypeText,
					Text: *content.TextString,
				})
			} else if content.Text != nil && content.Text.Text != "" {
				textParts = append(textParts, content.Text.Text)
				multiContent = append(multiContent, openai.ChatMessagePart{
					Type: openai.ChatMessagePartTypeText,
					Text: content.Text.Text,
				})

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[Copilot]

The SwapBranchToMain function has complex branching logic handling multiple scenarios (existing MAIN branch record vs. only MAIN items). This complexity makes the function harder to maintain and test. Consider extracting the backup creation logic into a separate helper function like "createMainBackup" to improve readability and testability.

[Copilot]

The error message "can only regenerate assistant messages" could be more descriptive. Consider changing it to "only assistant messages can be regenerated, cannot regenerate user or system messages" to provide clearer guidance about what went wrong.

Suggested change

	return nil, platformerrors.NewError(ctx, platformerrors.LayerDomain, platformerrors.ErrorTypeValidation, "can only regenerate assistant messages", nil, "b2c3d4e5-f6a7-4b8c-9d0e-1f2a3b4c5d6e")
	return nil, platformerrors.NewError(ctx, platformerrors.LayerDomain, platformerrors.ErrorTypeValidation, "only assistant messages can be regenerated, cannot regenerate user or system messages", nil, "b2c3d4e5-f6a7-4b8c-9d0e-1f2a3b4c5d6e")