Drupal 9 compatibility issues & issue with existing groups not inheriting the new group role permissions

Problem with Drupal 9 compatibility

Thanks for creating this module! It looks great though we have some issues with it. :-)

The module doesn't work as it is now with Drupal 9.

Trying to add an user to the group produces the following error:

messageNotice: Undefined index: handler_settings in Drupal\group_roles_management\Plugin\EntityReferenceSelection\GroupTypeRoleSelection->buildEntityQuery() (line 28 of modules/contrib/group_roles_management/src/Plugin/EntityReferenceSelection/GroupTypeRoleSelection.php).

You can fix this by changing the following:
$group_type_id = $this->configuration['handler_settings']['group_type_id'];
to:
$group_type_id = $this->configuration['group_type_id'];

But fixing that, another error pops up:

Error: Call to a member function getTranslationFromContext() on null in Drupal\group_roles_management\Plugin\EntityReferenceSelection\GroupTypeRoleSelection->getReferenceableEntities() (line 76 of modules/contrib/group_roles_management/src/Plugin/EntityReferenceSelection/GroupTypeRoleSelection.php).

And even after fixing that, there are issues with setting the roles.

If you get the correct role listing to display in the group member edit screen, there will be an issue with the following workflow:
- Create a group with two roles "Editor" and "Admin"
- Allow Editor role to manage the Editor-role but not Admin
- Now edit an user who has the Admin role (you won't see the user having an admin role) and hit save
- That user now doesn't have the Admin-role anymore because the save just stored the values in the form.

Problem with existing groups

After enabling this module, you can edit the role permissions for existing groups but these aren't stored in the correct format in the backend somehow. So you see your role based permissions in the Group Type Permissions screen but whenever you call functions like $group->hasPermission("manage members with role {$role_id}", $account) they will always return false for existing groups.

If you add a new group, there are no issues with this.