Added Service contact_link column

This is going to be used for for the document download citizen landing
page, a service will add a contact link
e.g. https://customerservicecontactnumber.uk/dwp/ which will allow the
user to contact the sending department if there is an error or any
issues with the download.

* Added the contact link to the model
* Added db migration script to add the column to the database

app/models.py

@@ -342,6 +342,7 @@ class Service(db.Model, Versioned):
     )
     crown = db.Column(db.Boolean, index=False, nullable=False, default=True)
     rate_limit = db.Column(db.Integer, index=False, nullable=False, default=3000)
+    contact_link = db.Column(db.String(255), nullable=True, unique=False)
 
     organisation = db.relationship(
         'Organisation',

migrations/versions/0196_service_contact_link.py

@@ -0,0 +1,23 @@
+"""
+
+Revision ID: 0196_service_contact_link
+Revises: 0195_ft_notification_timestamps
+Create Date: 2018-05-31 15:01:32.977620
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = '0196_service_contact_link'
+down_revision = '0195_ft_notification_timestamps'
+
+
+def upgrade():
+    op.add_column('services', sa.Column('contact_link', sa.String(length=255), nullable=True))
+    op.add_column('services_history', sa.Column('contact_link', sa.String(length=255), nullable=True))
+
+
+def downgrade():
+    op.drop_column('services_history', 'contact_link')
+    op.drop_column('services', 'contact_link')