Add new endpoint to add support to proxy requests to build's services

As a part of https://gitlab.com/gitlab-org/gitlab-ee/issues/5276 we need a new endpoint in Workhorse that can proxy requests to the GitLab Runner. It also has to handle transparently websocket requets.

Follow-up issue for proxying regular HTTP requests: #216 (closed)

changed milestone to %11.9

added Category:Web IDE Create [DEPRECATED] Deliverable workhorse labels

changed weight to 3

/cc @DouweM

added backend label

added to epic &167 (closed)

What does "proxy requests bidirectionaly" mean?

I tried finding it in https://gitlab.com/gitlab-org/gitlab-ee/issues/5276#note_130070917 where I see two options:

• client (web IDE) makes HTTP requests to runner
• client establishes websocket connection to runner

Neither looks "bidirectional" to me. The whole thing sounds more like "web IDE can connect to a CI runner just like the web terminal can connect to a kubernetes container". Is that correct?

changed the description

@jacobvosmaer-gitlab you're right. In this context, the bidirectionality is tightly related to handle websockets connections as we do with the web ide terminal. I've updated the desc to remove this term and avoid ambiguity.

added workflowin dev label

mentioned in merge request !370 (merged)

added workflowin review label and removed workflowin dev label

mentioned in issue #216 (closed)

marked this issue as related to #216 (closed)

changed the description

changed milestone to %11.11