API Update messaging

* Added <pipelinelink> so that messages can direct users to the log, and have added it to the error message.
* Added <commitsha> so that messages can distinguish which commit is being made.
* Improved wording on user confirmation message, so that it's made apparent that you need to login to provide approvals.
* Emergency rollback step will message the success message when it starts, rather than waiting for the timeout to occur. This means that once the deployment has actually complete and rollback is ready, the initiator is notified straight away.
* Fixed rollback step so that the initiator is set as the author.
* Removed a temporary hack which is no longer necessary.