Add external CI service/integration build link to the MR widget

Continuation of https://gitlab.com/gitlab-org/gitlab-ce/issues/30714 and inspired while working on https://gitlab.com/gitlab-org/gitlab-ce/issues/33287

Add external CI service/integration build link to the MR widget.

Why?

Currently when an external CI build fails, there isn't an easy way to jump to the external service itself and find out why it failed.

Potential solutions

We have the build_page method in CiService which returns a link to the build.

If we want something like the PoC, it will require some BE work to shove the data in the MR pipeline attribute properly.

PoC/mockup

Quick and dirty PoC: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13975

To compare against what the normal GitLab CI pipeline section of the MR widget looks like


cc @victorwu @ayufan

Edited by Eric Eastwood