Support multipart/form-data and form-urlencoded as Request content

[kdavisk6]

Feign provides support for the mime-type: multipart/form-data through the feign-form extension. Many APIs and other legacy system support application/x-www-form-urlencoded and multipart/form-data as a means to accept content.

Feignx should provide support for these types without the need for an extension. Ideally this support would be enabled by sniffing the Content-Type header provided by the user on the method signature. Another option is to create a specific annotation for form parameters, such as @FormParam.

Supporting forms this way to bringing parity between Feignx and Feign.