springboot Enhance autoconfiguration support for Spring HATEOAS.

DO NOT MERGE

So far it has this: * Provide CodecCustomizer to support WebClient. * Provide RestTemplateCustomizer. * Provide CodecCustomizer to suppor WebTestClient.

Add test cases to verify: * Autoconfiguration above works. * Verify RestTemplateCustomizer is also picked up for TestRestTemplate.

However, HypermediaTestRestTemplateTests, which passed briefly, now won't compile, complaining about:

> Task :spring-boot-project:spring-boot-test-autoconfigure:compileTestJava
/Users/gturnquist/src/spring-boot/spring-boot-project/spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/hateoas/HypermediaTestRestTemplateTests.java:52: error: cannot find symbol
    @ImportAutoConfiguration({HypermediaAutoConfiguration.class, RestTemplateAutoConfiguration.class})
     ^
  symbol:   class ImportAutoConfiguration
  location: class HypermediaTestRestTemplateTests
/Users/gturnquist/src/spring-boot/spring-boot-project/spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/hateoas/HypermediaTestRestTemplateTests.java:53: error: cannot find symbol
    @Configuration(proxyBeanMethods = false)
     ^
  symbol:   class Configuration
  location: class HypermediaTestRestTemplateTests
/Users/gturnquist/src/spring-boot/spring-boot-project/spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/hateoas/HypermediaTestRestTemplateTests.java:54: error: cannot find symbol
    @EnableHypermediaSupport(type = HypermediaType.HAL)
     ^
  symbol:   class EnableHypermediaSupport
  location: class HypermediaTestRestTemplateTests
3 errors
> Task :spring-boot-project:spring-boot-test-autoconfigure:compileTestJava FAILED
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':spring-boot-project:spring-boot-test-autoconfigure:compileTestJava'.
> Compilation failed; see the compiler error output for details.
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
* Get more help at https://help.gradle.org
BUILD FAILED in 2m 24s

Comment From: gregturn

Split up this work into multiple PRs.