Buggy checks on session and role-invite and owner role

[shreyanshdwivedi]

Describe the bug

• If an organizer of an event tries to delete any user who has accepted role invite, then 422 error is produced - Unprocessable Entity: "Only users can edit their own status" on FE
  This is due to a check on server -

if user:
            if not has_access('is_user_itself', user_id=user.id):
                raise UnprocessableEntity({'source': ''}, "Only users can edit their own status")

• When the locked status is tried to be changed by organizer, error is raised.
  KeyError: event_id
• missing owner from admin_statistics_api
• missing permissions for owner

Expected behavior

• The user should be deleted in first case
• The session should be updated
• owner to be added to admin_statistics_api
• add permissions for owner

Additional context

On it