[Improvement] Possible NPE in revokeRolesFromUser error handling when request body is null

What would you like to be improved?

PermissionOperations.revokeRolesFromUser can throw an unintended NullPointerException in its catch block. When the RoleRevokeRequest request is null (for example, due to an empty/invalid request body), the handler calls request.getRoleNames() while building the error response. This masks the original failure path and returns an unhelpful internal error.

How should we improve?

Make catch-block argument construction null-safe before calling ExceptionHandlers:

• Build role-name string with a null guard, e.g. empty string when request == null (or when role names are null).
• Reuse that safe value in handleUserPermissionOperationException(...).
• If needed, apply the same pattern to similar endpoints (grant/revoke for user/group) to avoid equivalent NPEs.

Here's a unit test to help:

@Test
public void testRevokeRolesFromUserWithNullRequest() throws Exception {
  PermissionOperations operations = new PermissionOperations();
  HttpServletRequest request = mock(HttpServletRequest.class);
  when(request.getAttribute(any())).thenReturn(null);
  FieldUtils.writeField(operations, "httpRequest", request, true);

  Response response = operations.revokeRolesFromUser("metalake1", "user1", null);
  Assertions.assertEquals(
      Response.Status.INTERNAL_SERVER_ERROR.getStatusCode(), response.getStatus());
}