Refactor code style and add tests for exception handling

Adjusted code style to align with consistent brace formatting and removed the null/blank check for `baseUrl` in the constructor. Added unit tests to verify exception handling in `CfDnsClient` for null arguments.

src/test/java/codes/thischwa/cf/CfClientTest.java

@@ -89,4 +89,10 @@ public class CfClientTest {
     client.recordDeleteTypeIfExists(z, sldStr, RecordType.A);
     assertThrows(CloudflareNotFoundException.class, () -> client.sldInfo(z, sldStr, RecordType.A));
   }
+
+  @Test
+  void testException() {
+   assertThrows(IllegalArgumentException.class, () -> new CfDnsClient(null, "key"));
+   assertThrows(IllegalArgumentException.class, () -> new CfDnsClient("email", null));
+  }
 }