Registry enhancement - Feature to add keycloak roles to the users

[shiva-rakshith]

Usecase scenario:
Creating a user in the registry will create a user in keycloak. currently, we don't have any feature in registry to add keycloak roles to users.

Adding keycloak roles to users, will help to give different privileges to users. For example, we can give access to different users to different APIs based on their roles, which can be extracted from JWT token(as it contains role information).

Sample request body with roles:

{
   "name": "Ravi kumar",
   "roles": ["teacher"],
   "email: "ravi.kumar@gmail.com",
   "phone": "9666505050"
}

The roles property should be of type List, as multiple roles can be assigned to a person.
Whatever the roles is passed in the request body, the same will be added to user in keycloak. If roles property is not define in the request body, registry will consider that as empty list and no role will be added.

Configuration changes:

1. Define roles in keycloak.
   (keycloak -> roles -> add role)

2. Add the 'view-realm' role to client(admin-api) to access the keycloak roles
   ( Keycloak -> open client(which is configured as client_id in application.yml) -> Service Account Roles -> Client Roles, select 'realm-management' -> Assign 'view-realm' role)

Future enhancements:

1. Instead of manually adding the roles in keycloak. Registry should able to add the roles(if not exist) programmatically.

Discussion link: Sunbird-RC/community#178