feat: [WIP] 🍰 Implement `JoinGroup`, `GroupMember`, `SwitchGroupMemberRole` Resolvers

Created by: Tirokk

🍰 Pullrequest

Implement JoinGroup, GroupMember, and SwitchGroupMemberRole resolvers.

Issues

• fixes #5188 (closed)
• fixes #5189 (closed)

Todo

• rename EnterGroup to JoinGroup
• change name SwitchGroupMemberRole to ChangeGroupMemberRole
• implement ChangeGroupMemberRole
  • add functionallity to join group with ChangeGroupMemberRole
    • test this
• test ChangeGroupMemberRole
  • general tests
  • check for has "updatedAt" newer as "createdAt"?
    • the GQL mutation would need this fields in the result for testing
    • !!! we decided to do it not yet
  • shall a switch to a role which the a member already has through a permission error?
    • !!! we decided to through no error
  • can an owner be degraded?
    • shall an owner can switch the role of another owner to a lower role yet?
    • or shall only an owner who gave the second owner the owner role downgrade themself?
    • !!! we decided an owner can not be degraded yet
• switch some group members role in seeding
• who can make a user joining a group
  • the user themselfs in case of groups of type public and closed
  • the admin/owner with an invite code in case of groups of type hidden
    • we decided that a hidden group can not be joined
      • !!! we decide a hidden group can only be joined by ChangeGroupMemberRole by an owner (no admin)
• cleanup: search Wolle