Remove use of OAuth password grant type

[nitin-vavdiya]

This is an enhancement ticket

Issue:

As per the current login flow, the frontend sends a username and password to the backend application and the backend authenticates the user using an OAuth grant-type password. This is not a recommended approach for many reasons.

Fix:

1. Use keycloak.js in front end application to support login with code flow. It also solves the token refresh problem
2. Remove login API from the backend application