added dd-254 model

atst/models/dd_254.py

@@ -0,0 +1,31 @@
+from sqlalchemy import Column, String
+from sqlalchemy.types import ARRAY
+from sqlalchemy.orm import relationship
+
+from atst.models import Base, types, mixins
+
+
+class DD254(Base, mixins.TimestampsMixin):
+    __tablename__ = "dd_254s"
+
+    id = types.Id()
+
+    certifying_official = Column(String)
+    co_title = Column(String)
+    co_address = Column(String)
+    co_phone = Column(String)
+    required_distribution = Column(ARRAY(String))
+
+    task_order = relationship("TaskOrder", uselist=False, backref="task_order")
+
+    def to_dictionary(self):
+        return {
+            c.name: getattr(self, c.name)
+            for c in self.__table__.columns
+            if c.name not in ["id"]
+        }
+
+    def __repr__(self):
+        return "<DD254(certifying_official='{}', task_order='{}', id='{}')>".format(
+            self.certifying_official, self.task_order.id, self.id
+        )