delete notification on user deletion (#658)

* delete notification on user deletion

fix #651

* use the correct id for deletion

* add regression test

* push helpers too

* revert CI changes

plume-models/src/notifications.rs

@@ -1,5 +1,5 @@
 use chrono::NaiveDateTime;
-use diesel::{self, ExpressionMethods, QueryDsl, RunQueryDsl};
+use diesel::{self, ExpressionMethods, JoinOnDsl, QueryDsl, RunQueryDsl};
 
 use comments::Comment;
 use follows::Follow;
@@ -7,7 +7,7 @@ use likes::Like;
 use mentions::Mention;
 use posts::Post;
 use reshares::Reshare;
-use schema::notifications;
+use schema::{follows, notifications};
 use users::User;
 use {Connection, Error, Result};
 
@@ -64,6 +64,16 @@ impl Notification {
             .map_err(Error::from)
     }
 
+    pub fn find_followed_by(conn: &Connection, user: &User) -> Result<Vec<Notification>> {
+        notifications::table
+            .inner_join(follows::table.on(notifications::object_id.eq(follows::id)))
+            .filter(notifications::kind.eq(notification_kind::FOLLOW))
+            .filter(follows::follower_id.eq(user.id))
+            .select(notifications::all_columns)
+            .load::<Notification>(conn)
+            .map_err(Error::from)
+    }
+
     pub fn count_for_user(conn: &Connection, user: &User) -> Result<i64> {
         notifications::table
             .filter(notifications::user_id.eq(user.id))