This commit refactors the application's error handling mechanism by introducing a new standardized error type, `types.NewAPIError`. It also renames common JSON utility functions for better clarity.
Previously, internal error handling was tightly coupled to the `dto.OpenAIError` format. This change decouples the internal logic from the external API representation.
Key changes:
- A new `types.NewAPIError` struct is introduced to serve as a canonical internal representation for all API errors.
- All relay adapters (OpenAI, Claude, Gemini, etc.) are updated to return `*types.NewAPIError`.
- Controllers now convert the internal `NewAPIError` to the client-facing `OpenAIError` format at the API boundary, ensuring backward compatibility.
- Channel auto-disable/enable logic is updated to use the new standardized error type.
- JSON utility functions are renamed to align with Go's standard library conventions (e.g., `UnmarshalJson` -> `Unmarshal`, `EncodeJson` -> `Marshal`).
- Remove global `RootUserEmail` variable
- Modify channel testing and user notification methods to use `GetRootUser()`
- Update user cache and notification service to use more consistent user base type
- Add new channel test notification type
- Introduce AutomaticDisableKeywords setting to dynamically control channel disabling
- Implement AC search for matching error messages against disable keywords
- Add frontend UI for configuring automatic disable keywords
- Update localization with new keyword-based channel disabling feature
- Refactor sensitive word and AC search logic to support multiple keyword lists
