feat: Adding support for SSE on the WebClient

[ehsavoie]

Motivation:

I needed to be able to process SSE events on the client side.

Conformance:

You should have signed the Eclipse Contributor Agreement as explained in https://github.com/eclipse/vert.x/blob/master/CONTRIBUTING.md
Please also make sure you adhere to the code style guidelines: https://github.com/vert-x3/wiki/wiki/Vert.x-code-style-guidelines

[vietj]

we need for now

• at least 1 integration test with WebClient
• SseBodyCodec and tests should be in vertx-web-common package instead where BodyCodec is

[tsegismont]

Thank you @ehsavoie !

How about moving SseEvent to the common module so that we could, later on, think about sse for the server without breaking things here?

cc @vietj

[ehsavoie]

@tsegismont maybe I could make the SseEvent toString to acutally create a 'valid'SSE string with the new lines

[vietj]

A few changes

[tsegismont]

Thank you @ehsavoie ! This looks great already. I think we need to make the new objects Vert.x API objects (annotated with @VertxGen or @DataObject).

Otherwise, they won't be available in generated bindings.

That might require a bit of refactoring, you can inspire from other codecs, like BodyCodec.

[tsegismont]

Thank you for the updates @ehsavoie !

[tsegismont]

Thank you @ehsavoie !

[tsegismont]

@vietj @ehsavoie do we intend to backport this to 4.x ? I believe we should take this into account while implementing the data object (regarding requirements of data objects like empty/copy/json constructors)

[tsegismont]

Any reason for not moving the test from web-common to web-client?

[ehsavoie]

@tsegismont I've move the test