add service broadcast provider restriction table

some services only send to one provider. This is a platform admin
setting to allow us to test integrations and providers manually without
affecting other broadcasts from different services.

one-to-one - a service can either send to all as normal, or send to only
one provider.

app/models.py

@@ -2472,3 +2472,22 @@ class BroadcastProviderMessage(db.Model):
     updated_at = db.Column(db.DateTime, nullable=True, onupdate=datetime.datetime.utcnow)
 
     UniqueConstraint(broadcast_event_id, provider)
+
+
+class ServiceBroadcastProviderRestriction(db.Model):
+    """
+    Most services don't send broadcasts. Of those that do, most send to all broadcast providers.
+    However, some services don't send to all providers. These services are test services that we or the providers
+    themselves use.
+
+    This table links those services. There should only be one row per service in this table, and this is enforced by
+    the service_id being a primary key.
+    """
+    __tablename__ = "service_broadcast_provider_restriction"
+
+    service_id = db.Column(UUID(as_uuid=True), db.ForeignKey('services.id'), primary_key=True, nullable=False)
+    service = db.relationship(Service, backref=db.backref("allowed_broadcast_provider", uselist=False))
+
+    provider = db.Column(db.String, nullable=False)
+
+    created_at = db.Column(db.DateTime, nullable=False, default=datetime.datetime.utcnow)

migrations/versions/0333_service_broadcast_provider.py

@@ -0,0 +1,28 @@
+"""
+
+Revision ID: 0333_service_broadcast_provider
+Revises: 0332_broadcast_provider_msg
+Create Date: 2020-12-01 17:03:18.209780
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+revision = '0333_service_broadcast_provider'
+down_revision = '0332_broadcast_provider_msg'
+
+
+def upgrade():
+    op.create_table(
+        'service_broadcast_provider_restriction',
+        sa.Column('service_id', postgresql.UUID(as_uuid=True), nullable=False),
+        sa.Column('provider', sa.String(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=False),
+        sa.ForeignKeyConstraint(['service_id'], ['services.id'], ),
+        sa.PrimaryKeyConstraint('service_id')
+    )
+
+
+def downgrade():
+    op.drop_table('service_broadcast_provider_restriction')