Add a type table for broadcast providers

This adds a type table for broadcast providers, which is the pattern we
follow with our models (e.g. we have a `broadcast_channel_types` table).

As well as the four providers, the migration populates it with `all`
which is the value that will replace `null` in a later change.

It should be safe to add the foreign key constraint to the
`service_broadcast_settings` in the same migration since the column is
still nullable and we don't have data in that column that is not in the
types table.

app/models.py

@@ -2553,7 +2553,7 @@ class ServiceBroadcastSettings(db.Model):
     channel = db.Column(
         db.String(255), db.ForeignKey('broadcast_channel_types.name'), nullable=False
     )
-    provider = db.Column(db.String, nullable=True)
+    provider = db.Column(db.String, db.ForeignKey('broadcast_provider_types.name'), nullable=True)
     created_at = db.Column(db.DateTime, nullable=False, default=datetime.datetime.utcnow)
     updated_at = db.Column(db.DateTime, nullable=True, onupdate=datetime.datetime.utcnow)
 
@@ -2564,6 +2564,12 @@ class BroadcastChannelTypes(db.Model):
     name = db.Column(db.String(255), primary_key=True)
 
 
+class BroadcastProviderTypes(db.Model):
+    __tablename__ = 'broadcast_provider_types'
+
+    name = db.Column(db.String(255), primary_key=True)
+
+
 class ServiceBroadcastProviderRestriction(db.Model):
     """
     TODO: Drop this table as no longer used

migrations/versions/0352_broadcast_provider_types.py

@@ -0,0 +1,32 @@
+"""
+
+Revision ID: 0352_broadcast_provider_types
+Revises: 0351_unique_key_annual_billing
+Create Date: 2021-05-05 15:07:22.146657
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+revision = '0352_broadcast_provider_types'
+down_revision = '0351_unique_key_annual_billing'
+
+PROVIDER_TYPES = ('ee', 'three', 'vodafone', 'o2', 'all')
+
+
+def upgrade():
+    op.create_table('broadcast_provider_types',
+                    sa.Column('name', sa.String(length=255), nullable=False),
+                    sa.PrimaryKeyConstraint('name'))
+    for provider in PROVIDER_TYPES:
+        op.execute(f"INSERT INTO broadcast_provider_types VALUES ('{provider}')")
+    op.create_foreign_key('service_broadcast_settings_provider_fkey',
+                          'service_broadcast_settings',
+                          'broadcast_provider_types',
+                          ['provider'],
+                          ['name'])
+
+
+def downgrade():
+    op.drop_constraint('service_broadcast_settings_provider_fkey', 'service_broadcast_settings', type_='foreignkey')
+    op.drop_table('broadcast_provider_types')

tests/conftest.py

@@ -120,7 +120,8 @@ def notify_db_session(notify_db, sms_providers):
                             "broadcast_status_type",
                             "invite_status_type",
                             "service_callback_type",
-                            "broadcast_channel_types"]:
+                            "broadcast_channel_types",
+                            "broadcast_provider_types"]:
             notify_db.engine.execute(tbl.delete())
     notify_db.session.commit()