Add configurable s3Key as an optional parameter

src/main/java/software/amazon/payloadoffloading/PayloadStore.java

@@ -20,6 +20,20 @@ public interface PayloadStore {
      */
     String storeOriginalPayload(String payload);
 
+    /**
+     * Stores payload in a store that has higher payload size limit than that is supported by original payload store.
+     *
+     * @param payload
+     * @param s3Key
+     * @return a pointer that must be used to retrieve the original payload later.
+     * @throws SdkClientException  If any internal errors are encountered on the client side while
+     *                                attempting to make the request or handle the response. For example
+     *                                if a network connection is not available.
+     * @throws S3Exception If an error response is returned by actual PayloadStore indicating
+     *                                either a problem with the data in the request, or a server side issue.
+     */
+    String storeOriginalPayload(String payload, String s3Key);
+
     /**
      * Retrieves the original payload using the given payloadPointer. The pointer must
      * have been obtained using {@link storeOriginalPayload}

src/main/java/software/amazon/payloadoffloading/S3BackedPayloadStore.java

@@ -22,7 +22,11 @@ public S3BackedPayloadStore(S3Dao s3Dao, String s3BucketName) {
     @Override
     public String storeOriginalPayload(String payload) {
         String s3Key = UUID.randomUUID().toString();
+        return storeOriginalPayload(payload, s3Key);
+    }
 
+    @Override
+    public String storeOriginalPayload(String payload, String s3Key) {
         s3Dao.storeTextInS3(s3BucketName, s3Key, payload);
         LOG.info("S3 object created, Bucket name: " + s3BucketName + ", Object key: " + s3Key + ".");
 

src/test/java/software/amazon/payloadoffloading/S3BackedPayloadStoreTest.java

@@ -49,6 +49,17 @@ public void testStoreOriginalPayloadOnSuccess() {
         assertEquals(expectedPayloadPointer.toJson(), actualPayloadPointer);
     }
 
+    @Test
+    public void testStoreOriginalPayloadWithS3KeyOnSuccess() {
+        String actualPayloadPointer = payloadStore.storeOriginalPayload(ANY_PAYLOAD, ANY_S3_KEY);
+
+        verify(s3Dao, times(1)).storeTextInS3(eq(S3_BUCKET_NAME), eq(ANY_S3_KEY),
+                eq(ANY_PAYLOAD));
+
+        PayloadS3Pointer expectedPayloadPointer = new PayloadS3Pointer(S3_BUCKET_NAME, ANY_S3_KEY);
+        assertEquals(expectedPayloadPointer.toJson(), actualPayloadPointer);
+    }
+
     @Test
     public void testStoreOriginalPayloadDoesAlwaysCreateNewObjects() {
         //Store any payload