add DVLA organisations to API

when services are created, they'll have a dvla_org_id of 001, or
HM Government. That can be changed later using a regular update call

migrations/versions/0072_add_dvla_orgs.py

@@ -0,0 +1,60 @@
+"""empty message
+
+Revision ID: 0072_add_dvla_orgs
+Revises: 0071_add_job_error_state
+Create Date: 2017-04-19 15:25:45.155886
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '0072_add_dvla_orgs'
+down_revision = '0071_add_job_error_state'
+
+from alembic import op
+import sqlalchemy as sa
+
+
+def upgrade():
+    ### commands auto generated by Alembic - please adjust! ###
+    op.create_table('dvla_organisation',
+        sa.Column('id', sa.String(), nullable=False),
+        sa.Column('name', sa.String(length=255), nullable=True),
+        sa.PrimaryKeyConstraint('id')
+    )
+
+    # insert initial values - HMG and Land Reg
+    op.execute("""
+        INSERT INTO dvla_organisation VALUES
+        ('001', 'HM Government'),
+        ('500', 'Land Registry')
+    """)
+
+    op.add_column('services', sa.Column('dvla_organisation_id', sa.String(), nullable=True))
+    op.add_column('services_history', sa.Column('dvla_organisation_id', sa.String(), nullable=True))
+
+    # set everything to be HMG for now
+    op.execute("UPDATE services SET dvla_organisation_id = '001'")
+    op.execute("UPDATE services_history SET dvla_organisation_id = '001'")
+
+    op.alter_column('services', 'dvla_organisation_id', nullable=False)
+    op.alter_column('services_history', 'dvla_organisation_id', nullable=False)
+
+    op.create_index(
+        op.f('ix_services_dvla_organisation_id'),
+        'services',
+        ['dvla_organisation_id'],
+        unique=False
+    )
+    op.create_index(
+        op.f('ix_services_history_dvla_organisation_id'),
+        'services_history',
+        ['dvla_organisation_id'],
+        unique=False
+    )
+
+    op.create_foreign_key(None, 'services', 'dvla_organisation', ['dvla_organisation_id'], ['id'])
+
+def downgrade():
+    op.drop_column('services_history', 'dvla_organisation_id')
+    op.drop_column('services', 'dvla_organisation_id')
+    op.drop_table('dvla_organisation')