Add ‘GP’ as an org type

Although their allowances are the same as what we call `nhs_local` it
makes more sense to store them separately because:
- we already present them as two separate choices to the user
- we may want to handle them differently in the future, eg in terms of
  what branding choices are available to them

migrations/versions/0305_add_gp_org_type.py

@@ -0,0 +1,42 @@
+import os
+
+"""
+
+Revision ID: 0305_add_gp_org_type
+Revises: 0304_remove_org_to_service
+Create Date: 2019-07-24 16:18:27.467361
+
+"""
+from alembic import op
+
+
+revision = '0305_add_gp_org_type'
+down_revision = '0304_remove_org_to_service'
+GP_ORG_TYPE_NAME = 'gp'
+
+
+def upgrade():
+    op.execute("""
+        INSERT INTO
+            organisation_types
+            (name, is_crown, annual_free_sms_fragment_limit)
+        VALUES
+            ('{}', false, 25000)
+    """.format(GP_ORG_TYPE_NAME))
+
+
+def downgrade():
+    op.execute("""
+        UPDATE
+            organisation
+        SET
+            organisation_type = 'nhs_local'
+        WHERE
+            organisation_type = '{}'
+    """.format(GP_ORG_TYPE_NAME))
+    op.execute("""
+        DELETE FROM
+            organisation_types
+        WHERE
+            name = '{}'
+    """.format(GP_ORG_TYPE_NAME))