Allow configuring shouldLogRequestHeader/shouldLogResponseHeader

[jkstrauss]

**Suppressing specific headers is cumbersome **
Certain headers should probably not be logged, e.g., Authorization.

Add configuration properties to include/exclude headers
Add the following list configurations:

• spring.cloud.openfeign.client.config.name.headers.request.include
• spring.cloud.openfeign.client.config.name.headers.request.exclude
• spring.cloud.openfeign.client.config.name.headers.response.include
• spring.cloud.openfeign.client.config.name.headers.response.exclude

The expected behavior would be to exclude any header in the exclude list, and only show header in the include list if any are present.

Alternatives: Making a custom component

@Component
    class MyFeignLoggerFactory implements FeignLoggerFactory {
      @Override
      public Logger create(Class<?> type) {
        return new Slf4jLogger(type) {
          @Override
          protected boolean shouldLogRequestHeader(String header) {
            return !"Authorization".equals(header);
          }
        };
      }
    }