add Group SQLAlchemy ORM model

Signed-off-by: Kevin Morris <kevr@0cost.org>

aurweb/models/group.py

+from sqlalchemy.orm import mapper
+
+from aurweb.schema import Groups
+
+
+class Group:
+    def __init__(self, Name: str = None):
+        self.Name = Name
+
+
+mapper(Group, Groups)

test/test_group.py

+import pytest
+
+from sqlalchemy.exc import IntegrityError
+
+from aurweb.db import create, delete, get_engine
+from aurweb.models.group import Group
+
+
+def test_group_creation():
+    get_engine()
+    group = create(Group, Name="Test Group")
+    assert bool(group.ID)
+    assert group.Name == "Test Group"
+    delete(Group, Group.ID == group.ID)
+
+
+def test_group_null_name_raises_exception():
+    from aurweb.db import session
+    with pytest.raises(IntegrityError):
+        create(Group)
+    session.rollback()