Bug/50677 users that are shared with a wp cannot be added as project members any more

[ulferts]

Removes Members on entities like WorkPackages from two scopes and by that:

• avoids them showing up in the administration page of a user where the current memberships in projects are listed:

• allows to add users as members with whom work packages inside the project have been shared before
• fixes showing the work package members in the members list: https://community.openproject.org/wp/50916

https://community.openproject.org/wp/50677

[klaustopher]

Would it maybe make sense that we add scopes on memberships?

scope :on_project, -> { where(entity: nil).where.not(project_id: nil) }
scope :global, -> { where(entity: nil).where(project_id: nil) }
scope :on_entity, -> { where.not(entity: nil, project_id: nil) }

Then we could use those instead of spreading where(entity: nil) in places outside of the model itself

[ulferts]

@klaustopher all the scopes should now be in as discussed.

[klaustopher]

Awesome!