Chore: Enable Users to create multiple accounts (#440)

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

Co-authored-by: Sojan Jose <sojan@pepalo.com>
Co-authored-by: Pranav Raj Sreepuram <pranavrajs@gmail.com>

app/views/api/v1/models/user.json.jbuilder

@@ -0,0 +1,12 @@
+json.id resource.id
+json.provider resource.provider
+json.uid resource.uid
+json.name resource.name
+json.nickname resource.nickname
+json.email resource.email
+json.account_id resource.account.id
+json.pubsub_token resource.pubsub_token
+json.role resource.role
+json.inviter_id resource.account_user.inviter_id
+json.confirmed resource.confirmed?
+json.avatar_url resource.avatar_url