Notification for first pipeline run after auto devops is automatically enabled
### Problem to solve
Once auto devops is enabled by default, some users may be unaware of this fact. Once they receive a failure email for a CI pipeline, they may be confused as to why something they never configured failed and was then disabled.
### Further details
An example flow (current state)
1. GitLab is released, with auto devops enabled by default
2. user pushes a commit
3. user received a CI failure message
### Proposal
When auto devops is enabled by default, send notification when:
1. The pipeline was successful
* inform user auto devops was enabled
* short blurb about what is auto devops
* link to documentation
* link to pipeline
* small blurb about k8s? (benefits of adding a cluster if not present)
2. The pipeline failed and auto devops was disabled.
* inform user auto devops was enabled
* short blurb about what is auto devops
* link to documentation
* inform user the pipeline ran and it failed
* link to pipeline
* inform user auto devops has been disabled
Who to notify?
* user to triggered the pipeline run
* owners?
### What does success look like, and how can we measure that?
(If no way to measure success, link to an issue that will implement a way to measure this)
### Links / references
issue