RANGER-5291 : 'User' role users api '/service/roles/roles' is giving 400 status

[dhavaljrajpara]

What changes were proposed in this pull request?

Steps to reproduce:

1. Create user having role as User eg user1

2. Create a policy eg hive and add the above the user, make the user as delegate admin.

3. Login as the user1 and edit the above created policy, try adding role in policy item. Observed the api "/service/roles/roles?roleNamePartial=" giving 400 status.

How was this patch tested?

The patch was tested by validating the new API "/service/roles/lookup/roles/names" from the UI end. The following checks were performed:

1. Validated CRUD operations on policies to ensure all role names are fetched correctly for users with different roles.
2. Validated CRUD operations on services to confirm role names are fetched correctly for different role users.
3. Validated CRUD operations in the Security Zone form to ensure the role names are being fetched properly.
4. Performed a search operation on the Report Page using the role names listed in the dropdown menu to ensure accurate filtering.