Add user objects for local test server (#2744)

Also don't try to do anything related to Google admin directory objects
when running the local test server, for obvious reasons

core/src/main/java/google/registry/config/CredentialModule.java

@@ -144,7 +144,6 @@ public abstract class CredentialModule {
       Duration tokenRefreshDelay,
       Clock clock) {
     GoogleCredentials signer = credentialsBundle.getGoogleCredentials();
-
     checkArgument(
         signer instanceof ServiceAccountSigner,
         "Expecting a ServiceAccountSigner, found %s.",

core/src/main/java/google/registry/ui/server/console/ConsoleUsersAction.java

@@ -165,7 +165,7 @@ public class ConsoleUsersAction extends ConsoleApiAction {
     User updatedUser = updateUserRegistrarRoles(email, registrarId, null);
 
     // User has no registrars assigned
-    if (updatedUser.getUserRoles().getRegistrarRoles().size() == 0) {
+    if (updatedUser.getUserRoles().getRegistrarRoles().isEmpty()) {
       try {
         directory.users().delete(email).execute();
       } catch (IOException e) {