[apache#5929] improvement(CLI): fix cli details command produce no ou…

…tput (apache#5941)

### What changes were proposed in this pull request?

If a user has no roles then no output is produced from `user\group
details` command, it should give some help information.

### Why are the changes needed?

Fix: apache#5929 

### Does this PR introduce _any_ user-facing change?

NO

### How was this patch tested?

```bash
bin/gcli.sh user details -m demo_metalake --user test_user
# output: User has no roles.

bin/gcli.sh group details -m demo_metalake --group group_no_role
# output: Groups has no roles.
```

---------

Co-authored-by: Qiming Teng <tengqm@outlook.com>

clients/cli/src/main/java/org/apache/gravitino/cli/commands/GroupDetails.java

@@ -60,7 +60,7 @@ public void handle() {
       exitWithError(exp.getMessage());
     }
 
-    String all = String.join(",", roles);
+    String all = roles.isEmpty() ? "The group has no roles." : String.join(",", roles);
 
     System.out.println(all.toString());
   }

clients/cli/src/main/java/org/apache/gravitino/cli/commands/UserDetails.java

@@ -60,7 +60,7 @@ public void handle() {
       exitWithError(exp.getMessage());
     }
 
-    String all = String.join(",", roles);
+    String all = roles.isEmpty() ? "The user has no roles." : String.join(",", roles);
 
     System.out.println(all.toString());
   }