add friend request id to notifications table

manifest

@@ -54,4 +54,5 @@ collapse_user_and_admin.sql
 default_gender_to_null.sql
 subscribe_email.sql
 notifications.sql
-notification_type_col_rename.sql
+notification_type_col_rename.sql
+notifications_add_friend_req_id.sql

up/notifications_add_friend_req_id.sql

@@ -0,0 +1 @@
+alter table notifications add COLUMN friend_request_id varchar(64) REFERENCES friend_requests(id);