Migrate Avro message converter artifacts

Migrate Avro message converter (non-schema-registry) artifacts
from Spring Cloud Schema Registry to Spring Cloud Function.

Resolves https://github.com/spring-cloud/spring-cloud-function/issues/732
Resolves #733

spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/converter/avro/AvroSchemaMessageConverterTests.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright 2021-2021 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.function.context.converter.avro;
+
+import java.util.Random;
+import java.util.UUID;
+import java.util.function.Function;
+
+import com.example.Sensor;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.WebApplicationType;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.builder.SpringApplicationBuilder;
+import org.springframework.cloud.function.context.FunctionCatalog;
+import org.springframework.cloud.function.context.catalog.SimpleFunctionRegistry;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageHeaders;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Soby Chacko
+ */
+public class AvroSchemaMessageConverterTests {
+
+	@Test
+	public void testAvroSchemaMessageConverter() {
+		try (ConfigurableApplicationContext context = new SpringApplicationBuilder(
+			SampleFunctionConfiguration.class).web(WebApplicationType.NONE).run(
+			"--spring.main.lazy-initialization=true")) {
+
+			FunctionCatalog functionCatalog = context.getBean(FunctionCatalog.class);
+			SimpleFunctionRegistry.FunctionInvocationWrapper function = functionCatalog.lookup("avroSensor");
+
+			Random random = new Random();
+			Sensor sensor = new Sensor();
+			sensor.setId(UUID.randomUUID().toString() + "-v1");
+			sensor.setAcceleration(random.nextFloat() * 10);
+			sensor.setVelocity(random.nextFloat() * 100);
+			sensor.setTemperature(random.nextFloat() * 50);
+
+			final AvroSchemaMessageConverter bean = context.getBean(AvroSchemaMessageConverter.class);
+			// Explicitly convert the Sensor to byte[]
+			final Message<?> message = bean.toMessage(sensor, new MessageHeaders(null));
+			// Now send with the sensor->byte[] converted payload.
+			final Sensor enrichedSensor = (Sensor) function.apply(message);
+
+			assertThat(enrichedSensor.getTemperature()).isEqualTo(sensor.getTemperature() + 5);
+		}
+	}
+
+	@EnableAutoConfiguration
+	@Configuration
+	protected static class SampleFunctionConfiguration {
+
+		@Bean
+		public Function<Sensor, Sensor> avroSensor() {
+			return s -> {
+				s.setTemperature(s.getTemperature() + 5);
+				return s;
+			};
+		}
+	}
+
+}

spring-cloud-function-context/src/test/resources/avro/sensor.avsc

@@ -0,0 +1,11 @@
+{
+  "namespace" : "com.example",
+  "type" : "record",
+  "name" : "Sensor",
+  "fields" : [
+    {"name":"id","type":"string"},
+    {"name":"temperature", "type":"float", "default":0.0},
+    {"name":"acceleration", "type":"float","default":0.0},
+    {"name":"velocity","type":"float","default":0.0}
+  ]
+}