Unit test user app

* adds unit test for User model and forms
* refactors functions from user_checks.py into User class and drops user_checks.py

intervention/forms/modals/share.py

@@ -12,7 +12,6 @@ from django.utils.translation import gettext_lazy as _
 from intervention.inputs import TextToClipboardInput
 from konova.forms.modals import BaseModalForm
 from konova.utils.message_templates import ENTRY_REMOVE_MISSING_PERMISSION
-from konova.utils.user_checks import is_default_group_only
 from user.models import Team, User
 
 
@@ -80,7 +79,7 @@ class ShareModalForm(BaseModalForm):
         teams = self.cleaned_data.get("teams", Team.objects.none())
 
         _is_valid = True
-        if is_default_group_only(self.user):
+        if self.user.is_default_group_only():
             shared_users = self.instance.shared_users
             shared_teams = self.instance.shared_teams