add Package SQLAlchemy ORM model

Additionally, add an optional **kwargs passing via make_relationship.
This allows us to use things like `uselist=False`, which was needed
for test/test_package.py.

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

aurweb/db.py

@@ -53,9 +53,10 @@ def make_random_value(table: str, column: str):
     return string
 
 
-def make_relationship(model, foreign_key, backref_):
+def make_relationship(model, foreign_key: str, backref_: str, **kwargs):
     return relationship(model, foreign_keys=[foreign_key],
-                        backref=backref(backref_, lazy="dynamic"))
+                        backref=backref(backref_, lazy="dynamic"),
+                        **kwargs)
 
 
 def query(model, *args, **kwargs):