delete External Accounts when user is deleted

lib/routes/admin.js

@@ -427,6 +427,16 @@ module.exports = function(crowi, app) {
         });
       });
     })
+    .then((userData) => {
+      // remove all External Accounts
+      ExternalAccount.remove({user: userData})
+      .then((err) => {
+        if (err) {
+          throw new Error(err.message);
+        }
+        return userData;
+      })
+    })
     .then((userData) => {
       return Page.removePageByPath(`/user/${username}`)
         .then(() => userData);