This commit introduces the MediaFile entity and updates the media attachments model, repositories, and related logic to reference MediaFile instead of storing file metadata directly in MediaAttachments. Controller, service, and SignalR request/response contracts are updated to support the new structure. Database configurations and validators are also adjusted accordingly. This refactor improves media management and normalization in the data model.
Introduces comprehensive unit tests for MessageService covering send, edit, and delete message scenarios. Adds and implements IGroupsRepository, IGroupsReader, and IGroupsWriter interfaces with method stubs in GroupRepository. Updates ChatGroup model with Description and ImageId fields, and registers GroupRepository in DI. Fixes parameter order in SendMessage record.