create, edit and use email branding instead of organisation

notable things that have been kept until migration is complete:

* passing in `organisation` to update_service will update email branding
* both `/email-branding` and `/organisation` hit the same code
* service endpoints still return organisation as well as email branding

app/email_branding/rest.py

@@ -0,0 +1,54 @@
+from flask import Blueprint, jsonify, request
+
+from app.dao.email_branding_dao import (
+    dao_create_email_branding,
+    dao_get_email_branding_options,
+    dao_get_email_branding_by_id,
+    dao_update_email_branding
+)
+from app.errors import register_errors
+from app.models import EmailBranding
+from app.email_branding.email_branding_schema import (
+    post_create_email_branding_schema,
+    post_update_email_branding_schema
+)
+from app.schema_validation import validate
+
+email_branding_blueprint = Blueprint('email_branding', __name__)
+register_errors(email_branding_blueprint)
+
+
+@email_branding_blueprint.route('', methods=['GET'])
+def get_email_branding_options():
+    email_branding_options = [o.serialize() for o in dao_get_email_branding_options()]
+    return jsonify(email_branding=email_branding_options)
+
+
+@email_branding_blueprint.route('/<uuid:email_branding_id>', methods=['GET'])
+def get_email_branding_by_id(email_branding_id):
+    email_branding = dao_get_email_branding_by_id(email_branding_id)
+    return jsonify(email_branding=email_branding.serialize())
+
+
+@email_branding_blueprint.route('', methods=['POST'])
+def create_email_branding():
+    data = request.get_json()
+
+    validate(data, post_create_email_branding_schema)
+
+    email_branding = EmailBranding(**data)
+
+    dao_create_email_branding(email_branding)
+    return jsonify(data=email_branding.serialize()), 201
+
+
+@email_branding_blueprint.route('/<uuid:email_branding_id>', methods=['POST'])
+def update_email_branding(email_branding_id):
+    data = request.get_json()
+
+    validate(data, post_update_email_branding_schema)
+
+    fetched_email_branding = dao_get_email_branding_by_id(email_branding_id)
+    dao_update_email_branding(fetched_email_branding, **data)
+
+    return jsonify(data=fetched_email_branding.serialize()), 200