Stop assuming "full name" in OAuth

Per a bug report, if an OAuth account name doesn't use a real name,
CDash will 500 if a space doesn't exist in the name.

Check for the space before trying to separate into first and last names.
If no space, use the whole string as the first name.

Fixes: Kitware#2435

app/Http/Controllers/OAuthController.php

@@ -36,7 +36,14 @@ public function callback(string $service): RedirectResponse|Redirector
         };
 
         $email =  $authUser->getEmail();
-        [$fname, $lname] = explode(" ", $authUser->getName() ?? '');
+        $name = $authUser->getName() ?? '';
+
+        // Check if name has space.  Avoid issue where username = "Real" name
+        if(str_contains(" ", $name)) {
+            [$fname, $lname] = explode(" ", $name);
+        } else {
+            [$fname, $lname] = [$name, ""];
+        }
 
         // TODO: What if, for whatever reason, there is more than one user found?
         $user = User::firstWhere('email', $email);