GH-460 Add support for function filtering

Added support for function filtering in the event there are more then one function in catalog. This is primarily to ensure that
we have a mechanism to specify which functions to export as web enpoints (instead of all)

Resolves #460

spring-cloud-function-adapters/spring-cloud-function-adapter-aws/src/test/java/org/springframework/cloud/function/adapter/aws/SpringBootRequestHandlerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2017-2020 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.
@@ -18,6 +18,7 @@ package org.springframework.cloud.function.adapter.aws;
 
 import java.util.function.Function;
 
+import org.junit.Before;
 import org.junit.Test;
 
 import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
@@ -36,6 +37,11 @@ public class SpringBootRequestHandlerTests {
 
 	private SpringBootRequestHandler<Foo, Bar> handler;
 
+	@Before
+	public void after() {
+		System.clearProperty("spring.cloud.function.definition");
+	}
+
 	@Test
 	public void functionBean() throws Exception {
 		this.handler = new SpringBootRequestHandler<Foo, Bar>(FunctionConfig.class);