feat: thank you screen

I picked a one hour expiration, and chose to clean issues stored after trying to deanonymized (whatever the result is). I also ignore potential errors when trying to deanonymized.

I had to change a few tests to make it work now that a global ngIf wraps the issue edition template, hence the trick to return a subject in spyOn(issueService, 'get'), then detect changes, then emit the issue...