Use proxy http://localhost:29418 with Pipelines endpoint

At the moment, the proxy http://localhost:29418 can be used in Bitbucket Pipelines builds in order to:

• push back to the same repo where the Pipelines build is running
• create reports and annotations

It has been requested that we make it possible to use this proxy with the following endpoint as well

/2.0/repositories/{workspace}/{repo_slug}/pipelines/

 in order to allow users to run a Pipeline via API from a Pipelines build, without the need to set up username and app password as authentication.