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

konova/utils/user_checks.py

@@ -1,37 +0,0 @@
-"""
-Author: Michel Peltriaux
-Organization: Struktur- und Genehmigungsdirektion Nord, Rhineland-Palatinate, Germany
-Contact: michel.peltriaux@sgdnord.rlp.de
-Created on: 02.07.21
-
-"""
-from user.models import User
-
-from konova.settings import ETS_GROUP, ZB_GROUP
-
-
-def in_group(user: User, group: str) -> bool:
-    """ Checks if the user is part of a group
-
-    Args:
-        user (User): The user object
-        group (str): The group's name
-
-    Returns:
-        bool
-    """
-    return user.groups.filter(
-        name=group
-    )
-
-
-def is_default_group_only(user: User) -> bool:
-    """ Checks if the user is only part of the default group
-
-    Args:
-        user (User): The user object
-
-    Returns:
-        bool
-    """
-    return not in_group(user, ZB_GROUP) and not in_group(user, ETS_GROUP)