Use Enum for request statuses

atst/models/request.py

@@ -24,3 +24,4 @@ class Request(Base):
 
     def set_status(self, status):
         self.status_events.append(status)
+

atst/models/request_status_event.py

@@ -1,5 +1,6 @@
-from sqlalchemy import Column, func, ForeignKey
-from sqlalchemy.types import DateTime, String, BigInteger
+from enum import Enum, auto
+from sqlalchemy import Column, func, ForeignKey, Enum as SQLAEnum
+from sqlalchemy.types import DateTime, BigInteger
 from sqlalchemy.schema import Sequence
 from sqlalchemy.dialects.postgresql import UUID
 
@@ -7,11 +8,18 @@ from atst.models import Base
 from atst.models.types import Id
 
 
+class RequestStatus(Enum):
+    STARTED = auto()
+    PENDING_FINANCIAL_VERIFICATION = auto()
+    PENDING_CCPO_APPROVAL = auto()
+    APPROVED = auto()
+
+
 class RequestStatusEvent(Base):
     __tablename__ = "request_status_events"
 
     id = Id()
-    new_status = Column(String())
+    new_status = Column(SQLAEnum(RequestStatus))
     time_created = Column(DateTime(timezone=True), server_default=func.now())
     request_id = Column(
         UUID(as_uuid=True), ForeignKey("requests.id", ondelete="CASCADE")