feat: Add Messages failover example (#122)

Author: SMadani

SNIPPETS.md

@@ -954,6 +954,22 @@ var response = client.getMessagesClient().sendMessage(
 );
 System.out.println("Message sent successfully. ID: "+response.getMessageUuid());
 ```
+### Send Message With Failover
+
+```java
+var response = client.getMessagesClient().sendMessage(
+        RcsTextRequest.builder()
+            .from(RCS_SENDER_ID).to(MESSAGES_TO_NUMBER)
+            .text("This is an RCS message sent via the Vonage Messages API")
+            .failover(SmsTextRequest.builder()
+                    .from(SMS_SENDER_ID).to(MESSAGES_TO_NUMBER)
+                    .text("This is an SMS sent using the Vonage Messages API.")
+                    .build()
+            )
+            .build()
+);
+System.out.println(response);
+```
 ### Messenger
 #### Send Messenger Text
 

src/main/java/com/vonage/quickstart/messages/SendMessageWithFailover.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2025 Vonage
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.vonage.quickstart.messages;
+
+import com.vonage.client.VonageClient;
+import com.vonage.client.messages.rcs.RcsTextRequest;
+import com.vonage.client.messages.sms.SmsTextRequest;
+import static com.vonage.quickstart.EnvironmentVariables.*;
+
+public class SendMessageWithFailover {
+    public static void main(String[] args) throws Exception {
+		VonageClient client = VonageClient.builder()
+				.applicationId(VONAGE_APPLICATION_ID)
+				.privateKeyPath(VONAGE_PRIVATE_KEY_PATH)
+				.build();
+
+		var response = client.getMessagesClient().sendMessage(
+				RcsTextRequest.builder()
+					.from(RCS_SENDER_ID).to(MESSAGES_TO_NUMBER)
+					.text("This is an RCS message sent via the Vonage Messages API")
+					.failover(SmsTextRequest.builder()
+							.from(SMS_SENDER_ID).to(MESSAGES_TO_NUMBER)
+							.text("This is an SMS sent using the Vonage Messages API.")
+							.build()
+					)
+					.build()
+		);
+		System.out.println(response);
+	}
+}