Batch assign groups

[skeet70]

Support a single call to assign a user to many groups as a member or admin.

AC, add UserOps for:

• user_add_groups
• user_add_groups_admin
• user_remove_groups
• user_remove_groups_admin

Blocked by: https://github.com/IronCoreLabs/ironcore-id/issues/1031, https://github.com/IronCoreLabs/ironcore-id/issues/1030, https://github.com/IronCoreLabs/ironcore-id/issues/1029, https://github.com/IronCoreLabs/ironcore-id/issues/1028