* Alerting: Create fewer contact points on migration
Previously a new contact point was created for every unique combination
of channels attached to any legacy alert. This was very hard to maintain,
requiring modifications in every generated contact point.
This change deduplicates the generated contact points to a more
reasonable state. There should now only be one contact point per legacy
channel, and we attached multiple contact points to a route by nesting
them. The sole exception to this is if there were multiple default
legacy channels, in which case we create a redundant contact point
containing all of them used only in the root policy. This allows for a
much simpler notification policy structure.
Co-authored-by: gotjosh <josue.abreu@gmail.com>
* Alerting: Add integration test for AddDashAlertMigration
* Add more targeted test cases
* Apply suggestions from code review
Co-authored-by: gotjosh <josue.abreu@gmail.com>
* Reorganize file and improve comments
* Replace custom sort+trim with go-cmp
* Add test for AddDashAlertMigration
* Rename test cases to standard format
* Apply suggestions from code review
Co-authored-by: gotjosh <josue.abreu@gmail.com>
* Remove test-only snapshots of PostableUserConfig et al.
* Organize imports
* Fix linting
Co-authored-by: gotjosh <josue.abreu@gmail.com>
