Group Management API & Admin UI

[Batacek]

Description

The domain model, database schema, and repository interface for groups already exist, but there is no way to manage them through the application — no API endpoints and no admin UI. Currently, groups can only be managed via direct SQL queries.

What already exists:

• Group entity (Domain/Entities/Group.cs)
• groups and user_groups tables in the database (create.sql)
• Admin panel already shows a highestPriorityGroup column in the users table (the data is there, just not manageable)

What is missing:

Backend:

• IGroupRepository interface (Application/Repositories/) with at least:
  • GetByGuidAsync, ListAsync, CreateAsync, UpdateAsync, DeleteAsync
  • GetMembersAsync(Guid groupGuid)
  • AddMemberAsync(Guid groupGuid, Guid userGuid, int priority)
  • RemoveMemberAsync(Guid groupGuid, Guid userGuid)
• GroupRepository implementation in Infrastructure/Persistence/PostgreSQL/Repositories/
• IGroupService and GroupService in Application/Services/
• API endpoints under /api/admin/groups (admin-only):
  • GET /api/admin/groups — list all groups
  • POST /api/admin/groups — create a group
  • DELETE /api/admin/groups/{name} — delete a group
  • GET /api/admin/groups/{name}/members — list members
  • POST /api/admin/groups/{name}/members — add a user to a group
  • DELETE /api/admin/groups/{name}/members/{username} — remove a user from a group
• Registration of IGroupRepository and IGroupService in HedgehogStartupExtensions.cs

Frontend (Admin.html):

• "Create Group" form (name, description)
• "Groups" table in the admin grid alongside Users and Servers, showing name, description, member count, and a delete button
• "Manage Members" section or inline expansion — add/remove users from a group with priority input
• Consistent style with the existing admin forms and tables
• New frontend already covers that

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Acceptance Criteria

• IGroupRepository and GroupRepository implemented and registered in DI
• IGroupService and GroupService implemented and registered in DI
• All /api/admin/groups endpoints working and protected by RequireRole("Admin")
• Admin UI allows creating and deleting groups
• Admin UI allows adding and removing users from groups with a priority value
• Deleting a group that has members fails gracefully or cascades correctly (consistent with the ON DELETE CASCADE already defined in the schema)
• Remove existing behavior (admin group → isAdmin = true)

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Notes

• The admin group is special. Deleting the admin group should either be blocked or require a confirmation warning.
• Priority in user_groups affects which group is shown as highestPriorityGroup in the users list — the UI should make this value editable when assigning a user to a group.
• Consider invalidating the relevant IInMemoryStore cache entries (Account) when group membership changes, since groups are loaded as part of the account object.