Only one header value of several is sent with MultipartForm body

[ilia1243]

Version

4.5.3

Context

The task is to send few values for the same header, e. g. using HttpRequest#putHeader(String, Iterable).

If using HttpRequest#sendForm() or HttpRequest#sendMultipartForm(), only the first value is sent.

If using just HttpRequest#send(), all values are sent.

Steps to reproduce

1. Execute on client side:

WebClient.getAbs("<URI>")
        .putHeader("Test", List.of("A", "B"))
        .sendForm(MultiMap.caseInsensitiveMultiMap())

2. Check the received headers on the server side.

Actual result:

Test: A

Expected result:

Test: A
Test: B

Extra

• Only one value is chosen in

  vertx-web/vertx-web-client/src/main/java/io/vertx/ext/web/client/impl/HttpContext.java

  Line 447 in 2a661ad

  requestOptions.putHeader(headerName, this.request.headers().get(headerName));

[ilia1243]

Suggested fix #2679