Remove the organisation_to_service table.

This table is no longer used or referenced in the code.
We can remove this mapping table now that the organisation to service relationship is handled by the foreign key in Services.

migrations/versions/0304_remove_org_to_service.py

@@ -0,0 +1,29 @@
+"""
+
+Revision ID: 0304_remove_org_to_service
+Revises: 0303_populate_services_org_id
+Create Date: 2019-08-15 14:49:00.754390
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+revision = '0304_remove_org_to_service'
+down_revision = '0303_populate_services_org_id'
+
+
+def upgrade():
+    op.drop_table('organisation_to_service')
+
+
+def downgrade():
+    op.create_table('organisation_to_service',
+                    sa.Column('service_id', postgresql.UUID(), autoincrement=False, nullable=False),
+                    sa.Column('organisation_id', postgresql.UUID(), autoincrement=False, nullable=False),
+                    sa.ForeignKeyConstraint(['organisation_id'], ['organisation.id'],
+                                            name='organisation_to_service_organisation_id_fkey'),
+                    sa.ForeignKeyConstraint(['service_id'], ['services.id'],
+                                            name='organisation_to_service_service_id_fkey'),
+                    sa.PrimaryKeyConstraint('service_id', name='organisation_to_service_pkey')
+                    )