fixes gh-907

Typo in example code for `DiscoveryClient`

`DiscoveryClient` field declared with name `discoveryClient` but `serviceUrl()` method uses `client`.

* rxjava-stream:
  Spring Mvc RxJava integration.

Support for Single via a ReturnValueHandler.
Support for Observable via SseEmitter.

fixes gh-902

fixes gh-749

typo fixed

* feignExpanders:
  Where a given String conversion is supported, register Feign Param.Expanders backed by a Feign-specific FormattingConversionService.

backed by a Feign-specific FormattingConversionService.

fixes gh-881

See gh-896

fixes gh-897

Fixes gh-891

8.15 version of Feign breaks VND content types

fixes gh-886

fixes gh-882

fixes gh-880

I'm not sure that is a good thing though.

Fixes gh-873

For compatiblity with Angel streams we only need to set the content
type explicitly.

Fixes gh-873

Consistent with Spring MVC (and untested up to now apparently).

Fixes gh-874

Fixes gh-872

i.e. user sends multiple files with the same parameter name.

Fixes gh-870

fixes gh-731

fixes gh-695

fixes gh-542