Add sequential numbering for broadcast messages

We need that to send broadcast messages using proprietary IBAG
format that Vodafone currently uses.

migrations/versions/0334_broadcast_message_number.py

@@ -0,0 +1,48 @@
+"""
+
+Revision ID: 0334_broadcast_message_number
+Revises: 0333_service_broadcast_provider
+Create Date: 2020-12-04 15:06:22.544803
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+revision = '0334_broadcast_message_number'
+down_revision = '0333_service_broadcast_provider'
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.execute("create sequence broadcast_provider_message_number_seq")
+    op.create_table(
+        'broadcast_provider_message_number',
+        sa.Column(
+            'broadcast_provider_message_number',
+            sa.Integer(),
+            server_default=sa.text("nextval('broadcast_provider_message_number_seq')"),
+            nullable=False
+        ),
+        sa.Column('broadcast_provider_message_id', postgresql.UUID(as_uuid=True), nullable=False),
+        sa.ForeignKeyConstraint(['broadcast_provider_message_id'], ['broadcast_provider_message.id'], ),
+        sa.PrimaryKeyConstraint('broadcast_provider_message_number')
+    )
+    op.execute(
+        """
+            INSERT INTO
+                broadcast_provider_message_number (broadcast_provider_message_id)
+            SELECT
+                id
+            FROM
+                broadcast_provider_message
+        """
+    )
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_table('broadcast_provider_message_number')
+    op.execute("drop sequence broadcast_provider_message_number_seq")
+    # ### end Alembic commands ###