add PackageRelation SQLAlchemy ORM model

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

aurweb/models/package_relation.py

@@ -0,0 +1,33 @@
+from sqlalchemy.orm import mapper
+
+from aurweb.db import make_relationship
+from aurweb.models.package import Package
+from aurweb.models.relation_type import RelationType
+from aurweb.schema import PackageRelations
+
+
+class PackageRelation:
+    def __init__(self, Package: Package = None,
+                 RelationType: RelationType = None,
+                 RelName: str = None, RelCondition: str = None,
+                 RelArch: str = None):
+        self.Package = Package
+        self.RelationType = RelationType
+        self.RelName = RelName  # nullable=False
+        self.RelCondition = RelCondition
+        self.RelArch = RelArch
+
+
+properties = {
+    "Package": make_relationship(Package, PackageRelations.c.PackageID,
+                                 "package_relations"),
+    "RelationType": make_relationship(RelationType,
+                                      PackageRelations.c.RelTypeID,
+                                      "package_relations")
+}
+
+mapper(PackageRelation, PackageRelations, properties=properties,
+       primary_key=[
+           PackageRelations.c.PackageID,
+           PackageRelations.c.RelTypeID
+       ])