Add Request.internal_comments

Using a one to one relationship to avoid the migration hell
that we're temporarily stuck in.

atst/models/__init__.py

@@ -16,3 +16,4 @@ from .environment import Environment
 from .attachment import Attachment
 from .request_revision import RequestRevision
 from .request_review import RequestReview
+from .request_internal_comment import RequestInternalComment

atst/models/request.py

@@ -46,6 +46,8 @@ class Request(Base):
         "RequestRevision", back_populates="request", order_by="RequestRevision.sequence"
     )
 
+    internal_comments = relationship("RequestInternalComment", uselist=False)
+
     @property
     def latest_revision(self):
         if self.revisions:

atst/models/request_internal_comment.py

@@ -0,0 +1,16 @@
+from sqlalchemy import Column, BigInteger, String, ForeignKey
+from sqlalchemy.orm import relationship
+
+from atst.models import Base
+
+
+class RequestInternalComment(Base):
+    __tablename__ = "request_internal_comments"
+
+    id = Column(BigInteger, primary_key=True)
+    text = Column(String())
+
+    user_id = Column(ForeignKey("users.id"), nullable=False)
+    user = relationship("User")
+
+    request_id = Column(ForeignKey("requests.id", ondelete="CASCADE"))