Add and populate crown column to services and services_history

- Added the boolean 'crown' column to services and services_history tables
- We populate this column in the same migration script by checking the
'organisation_type' of a service

migrations/versions/0149_add_crown_to_services.py

@@ -0,0 +1,42 @@
+"""
+
+Revision ID: 0149_add_crown_column_to_services
+Revises: 0148_add_letters_as_pdf_svc_perm
+Create Date: 2017-12-04 12:13:35.268712
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = '0149_add_crown_to_services'
+down_revision = '0148_add_letters_as_pdf_svc_perm'
+
+
+def upgrade():
+    op.add_column('services', sa.Column('crown', sa.Boolean(), nullable=True))
+    op.execute("""
+        update services set crown = True
+        where organisation_type = 'central'
+    """)
+    op.execute("""
+        update services set crown = False
+        where crown is null
+    """)
+    op.alter_column('services', 'crown', nullable=False)
+
+    op.add_column('services_history', sa.Column('crown', sa.Boolean(), nullable=True))
+    op.execute("""
+        update services_history set crown = True
+        where organisation_type = 'central'
+    """)
+    op.execute("""
+        update services_history set crown = False
+        where crown is null
+    """)
+    op.alter_column('services_history', 'crown', nullable=False)
+
+
+def downgrade():
+    op.drop_column('services', 'crown')
+    op.drop_column('services_history', 'crown')