Chore: Scope URLs with account_id (#601)

* Chore: Enable Users to create multiple accounts

Addresses: #402
- migrations to split roles and other attributes from users table
- make changes in code to accommodate this change

Co-authored-by: Pranav Raj Sreepuram <pranavrajs@gmail.com>

app/views/api/v1/accounts/webhooks/_webhook.json.jbuilder

@@ -0,0 +1,9 @@
+json.id webhook.id
+json.url webhook.url
+json.account_id webhook.account_id
+if webhook.inbox
+  json.inbox do
+    json.id webhook.inbox.id
+    json.name webhook.inbox.name
+  end
+end