Set folder permissions when creating and accepting invites to services

Added a folder permissions form to the page to invite users to services.
This only shows if the service has 'edit_folder_permissions' enabled,
and all folder checkboxes are checked by default. This change means that
InviteApiClient.create_invite now sends folder_permissions through to
notifications_api (so invites get created with folder permissions).

Started passing the folder_permissions through to notifications-api when
accepting an invite. This changes UserApiClient.add_user_to_service to
send folder_permissions to notifications_api so that new users get folder
permissions when they are added to the service.

app/notify_client/invite_api_client.py

@@ -12,7 +12,13 @@ class InviteApiClient(NotifyAdminAPIClient):
 
         self.admin_url = app.config['ADMIN_BASE_URL']
 
-    def create_invite(self, invite_from_id, service_id, email_address, permissions, auth_type):
+    def create_invite(self,
+                      invite_from_id,
+                      service_id,
+                      email_address,
+                      permissions,
+                      auth_type,
+                      folder_permissions):
         data = {
             'service': str(service_id),
             'email_address': email_address,
@@ -20,6 +26,7 @@ class InviteApiClient(NotifyAdminAPIClient):
             'permissions': ','.join(sorted(translate_permissions_from_admin_roles_to_db(permissions))),
             'auth_type': auth_type,
             'invite_link_host': self.admin_url,
+            'folder_permissions': folder_permissions,
         }
         data = _attach_current_user(data)
         resp = self.post(url='/service/{}/invite'.format(service_id), data=data)