Add mailPassword table

This table stores email credentials for users using apps which use the
email addon

src/users.js

@@ -266,6 +266,7 @@ async function del(user, auditSource) {
         { query: 'DELETE FROM groupMembers WHERE userId = ?', args: [ user.id ] },
         { query: 'DELETE FROM tokens WHERE identifier = ?', args: [ user.id ] },
         { query: 'DELETE FROM appPasswords WHERE userId = ?', args: [ user.id ] },
+        { query: 'DELETE FROM mailPasswords WHERE userId = ?', args: [ user.id ] },
         { query: 'DELETE FROM passkeys WHERE userId = ?', args: [ user.id ] },
         { query: 'DELETE FROM users WHERE id = ?', args: [ user.id ] }, // keep this the last query as we check affectedRows below
     ];