Fixed double conversion issue

- removed custom conversion from In/Out interceptors delegating everything to the available  MessageConverters
- added initial version of content-type TCK to validate various content-type conversion scenarious
- added initial content-type conversion matrix to the WIKI https://github.com/spring-cloud/spring-cloud-stream/wiki/Content-type-conversion-matrix

Resolves #1130
Resolves #1071

spring-cloud-stream-integration-tests/src/test/java/org/springframework/cloud/stream/config/DefaultHeaderPropagationWithApplicationProvidedHeaderTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017 the original author or authors.
+ * Copyright 2017-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -73,7 +73,7 @@ public class DefaultHeaderPropagationWithApplicationProvidedHeaderTests {
 
 		@ServiceActivator(inputChannel = "input", outputChannel = "output")
 		public Message<?> consume(String data) {
-			return MessageBuilder.withPayload(data).setHeader(MessageHeaders.CONTENT_TYPE, "custom/header").build();
+			return MessageBuilder.withPayload(data).setHeader(MessageHeaders.CONTENT_TYPE, "text/plain").build();
 		}
 
 	}

spring-cloud-stream-integration-tests/src/test/java/org/springframework/cloud/stream/config/InboundJsonToTupleConversionTest.java

@@ -16,6 +16,7 @@
 
 package org.springframework.cloud.stream.config;
 
+import java.nio.charset.StandardCharsets;
 import java.util.concurrent.TimeUnit;
 
 import org.junit.Test;
@@ -58,11 +59,11 @@ public class InboundJsonToTupleConversionTest {
 		testProcessor.input().send(MessageBuilder.withPayload("{'name':'foo'}")
 				.build());
 		@SuppressWarnings("unchecked")
-		Message<String> received = (Message<String>) ((TestSupportBinder) binderFactory.getBinder(null, MessageChannel.class))
+		Message<byte[]> received = (Message<byte[]>) ((TestSupportBinder) binderFactory.getBinder(null, MessageChannel.class))
 				.messageCollector().forChannel(testProcessor.output()).poll(1, TimeUnit.SECONDS);
 		assertThat(received).isNotNull();
-
-		assertThat(TupleBuilder.fromString(new String(received.getPayload()))).isEqualTo(TupleBuilder.tuple().of("name", "foo"));
+		String payload = new String(received.getPayload(), StandardCharsets.UTF_8);
+		assertThat(TupleBuilder.fromString(payload)).isEqualTo(TupleBuilder.tuple().of("name", "foo"));
 	}
 
 	@EnableBinding(Processor.class)

spring-cloud-stream-integration-tests/src/test/java/org/springframework/cloud/stream/config/LegacyContentTypeTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2017 the original author or authors.
+ * Copyright 2015-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 
 package org.springframework.cloud.stream.config;
 
+import java.nio.charset.StandardCharsets;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 
@@ -54,8 +55,8 @@ public class LegacyContentTypeTests {
 		MessageHandler messageHandler = new MessageHandler() {
 			@Override
 			public void handleMessage(Message<?> message) throws MessagingException {
-				assertThat(message.getPayload()).isInstanceOf(String.class);
-				assertThat(message.getPayload()).isEqualTo("{\"message\":\"Hi\"}");
+				assertThat(message.getPayload()).isInstanceOf(byte[].class);
+				assertThat(new String(((byte[])message.getPayload()), StandardCharsets.UTF_8)).isEqualTo("{\"message\":\"Hi\"}");
 				assertThat(message.getHeaders().get(MessageHeaders.CONTENT_TYPE).toString()).isEqualTo("application/json");
 				latch.countDown();
 			}
@@ -63,7 +64,6 @@ public class LegacyContentTypeTests {
 		testSink.input().subscribe(messageHandler);
 		testSink.input().send(MessageBuilder.withPayload("{\"message\":\"Hi\"}".getBytes())
 							.setHeader(BinderHeaders.BINDER_ORIGINAL_CONTENT_TYPE, "application/json")
-							.setHeader(BinderHeaders.SCST_VERSION, "1.x")
 							.build());
 		assertThat(latch.await(10, TimeUnit.SECONDS)).isTrue();
 		testSink.input().unsubscribe(messageHandler);

spring-cloud-stream-integration-tests/src/test/java/org/springframework/cloud/stream/config/contentType/ContentTypeTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017 the original author or authors.
+ * Copyright 2017-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -40,7 +40,6 @@ import org.springframework.cloud.stream.test.binder.MessageCollector;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.integration.support.MessageBuilder;
 import org.springframework.messaging.Message;
-import org.springframework.messaging.MessageDeliveryException;
 import org.springframework.messaging.MessageHeaders;
 import org.springframework.messaging.SubscribableChannel;
 import org.springframework.messaging.handler.annotation.Headers;
@@ -229,7 +228,7 @@ public class ContentTypeTests {
 			assertThat(message.getPayload()).isEqualTo(user.toString());
 		}
 	}
-
+	
 	@Test
 	public void testSendTuple() throws Exception {
 		try (ConfigurableApplicationContext context = SpringApplication.run(
@@ -313,7 +312,7 @@ public class ContentTypeTests {
 		}
 	}
 
-	@Test(expected=MessageDeliveryException.class)
+	@Test
 	public void testReceiveKryoWithHeadersOverridingDefault() throws Exception{
 		try (ConfigurableApplicationContext context = SpringApplication.run(
 				SinkApplication.class, "--server.port=0",

spring-cloud-stream-integration-tests/src/test/resources/org/springframework/cloud/stream/config/inboundjsontuple/inbound-json-tuple.properties

@@ -1 +1,2 @@
 spring.cloud.stream.bindings.input.content-type=application/x-spring-tuple
+spring.cloud.stream.bindings.output.content-type=application/x-spring-tuple