Have permissions decorators check user signed in

Rather than force us to write the decorators in a specific order let’s
just have one decorator call the other. This should make fewer lines of
code, and fewer annoying test failures. It also means that the same way
of raising a `401` (through the `current_app` method) is used
everywhere.

app/main/views/add_service.py

@@ -1,11 +1,11 @@
 from flask import current_app, redirect, render_template, session, url_for
-from flask_login import current_user, login_required
+from flask_login import current_user
 from notifications_python_client.errors import HTTPError
 
 from app import billing_api_client, service_api_client
 from app.main import main
 from app.main.forms import CreateServiceForm
-from app.utils import email_safe, user_is_gov_user
+from app.utils import email_safe, user_is_gov_user, user_is_logged_in
 
 
 def _create_service(service_name, organisation_type, email_from, form):
@@ -44,7 +44,7 @@ def _create_example_template(service_id):
 
 
 @main.route("/add-service", methods=['GET', 'POST'])
-@login_required
+@user_is_logged_in
 @user_is_gov_user
 def add_service():
     form = CreateServiceForm(