Introduced:
* Request Request.headers(Consumer<HttpFields.Mutable>).
This allows applications to modify the headers, and chain calls.
It also delegates the precise semantic of put/add/remove/clear to HttpFields, so there is no API duplication.
* HttpRequest.header(HttpField) to efficiently add fields while normalizing the request (only used in implementation).
* HttpResponse.header(HttpField) to efficiently add fields while parsing the response (only used in implementation).
This pairs with HttpResponse.trailer(HttpField).
* HttpResponse.headers(Consumer<HttpFields.Mutable>) to modify the fields after they have been populated (only used in tests).
Removed:
* Request.[set,add,put,remove], replaced by headers(Consumer<HttpFields.Mutable>).
Deprecated:
* Request.header(String, String)
* Request.header(HttpHeader, String)
Both replaced by headers(Consumer<HttpFields.Mutable>) with clearer semantic for add/put/remove.
All the rest is code cleanup to remove the usage of the deprecated header() methods.
Signed-off-by: Simone Bordet <simone.bordet@gmail.com>