refactor(output): share the JSON, created-resource and batch tails

Mutations end with a.jsonResult or a.created instead of hand-rolled
--json branches, the two identical jsonResult/writeMutationJSON helpers
become one, and writeBatchJSON checks --json itself so batch commands
share one tail.

Signed-off-by: bircni <bircni@icloud.com>

internal/app/admin_users.go

@@ -280,10 +280,7 @@ $ tea admin user create ci-bot --email ci@example.com --password-file pw.txt --m
 			return err
 		}
 		a.done(cmd, "Created user %s", user.Username)
-		if err := a.printURL(cmd, user.URL); err != nil {
-			return err
-		}
-		return a.jsonResult(cmd, user)
+		return a.created(cmd, user, user.URL)
 	}
 	return command
 }