Alerting: Add alert pausing feature (#60734)

* Add field in alert_rule model, add state to alert_instance model, and state to eval

* Remove paused state from eval package

* Skip paused alert rules in scheduler

* Add migration to add is_paused field to alert_rule table

* Convert to postable alerts only if not normal, pernding, or paused

* Handle paused eval results in state manager

* Add Paused state to eval package

* Add paused alerts logic in scheduler

* Skip alert on scheduler

* Remove paused status from eval package

* Apply suggestions from code review

Co-authored-by: George Robinson <george.robinson@grafana.com>

* Remove state

* Rethink schedule and manager for paused alerts

* Change return to continue

* Remove unused var

* Rethink alert pausing

* Paused alerts storing annotations

* Only add one state transition

* Revert boolean method renaming refactor

* Revert take image refactor

* Make registry errors public

* Revert method extraction for getting a folder title

* Revert variable renaming refactor

* Undo unnecessary changes

* Revert changes in test

* Remove IsPause check in PatchPartiLAlertRule function

* Use SetNormal to set state

* Fix text by returning to old behaviour on alert rule deletion

* Add test in schedule_unit_test.go to test ticks with paused alerts

* Add coment to clarify usage of context.Background()

* Add comment to clarify resetStateByRuleUID method usage

* Move rule get to a more limited scope

* Update pkg/services/ngalert/schedule/schedule.go

Co-authored-by: George Robinson <george.robinson@grafana.com>

* rum gofmt on pkg/services/ngalert/schedule/schedule.go

* Remove defer cancel for context

* Update pkg/services/ngalert/models/instance_test.go

Co-authored-by: Santiago <santiagohernandez.1997@gmail.com>

* Update pkg/services/ngalert/models/testing.go

Co-authored-by: Santiago <santiagohernandez.1997@gmail.com>

* Update pkg/services/ngalert/schedule/schedule_unit_test.go

Co-authored-by: Santiago <santiagohernandez.1997@gmail.com>

* Update pkg/services/ngalert/schedule/schedule_unit_test.go

Co-authored-by: Santiago <santiagohernandez.1997@gmail.com>

* Update pkg/services/ngalert/models/instance_test.go

Co-authored-by: Santiago <santiagohernandez.1997@gmail.com>

* skip scheduler rule state clean up on paused alert rule

* Update pkg/services/ngalert/schedule/schedule.go

Co-authored-by: Santiago <santiagohernandez.1997@gmail.com>

* Fix mock in test

* Add (hopefully) final suggestions

* Use error channel from recordAnnotationsSync to cancel context

* Run make gen-cue

* Place pause alert check in channel update after version check

* Reduce branching un update channel select

* Add if for error and move code inside if in state manager ResetStateByRuleUID

* Add reason to logs

* Update pkg/services/ngalert/schedule/schedule.go

Co-authored-by: George Robinson <george.robinson@grafana.com>

* Do not delete alert rule routine, just exit on eval if is paused

* Reduce branching and create-close a channel to avoid deadlocks

* Separate state deletion and state reset (includes history saving)

* Add current pause state in rule route in scheduler

* Split clearState and bring errCh closer to RecordStatesAsync call

* Change rule to ruleMeta in RecordStatesAsync

* copy state to be able to modify it

* Add timeout to context creation

* Shorten the timeout

* Use resetState is rule is paused and deleteState if rule is not paused

* Remove Empty state reason

* Save every rule change in historian

* Add tests for DeleteStateByRuleUID and ResetStateByRuleUID

* Remove useless line

* Remove outdated comment

Co-authored-by: George Robinson <george.robinson@grafana.com>
Co-authored-by: Santiago <santiagohernandez.1997@gmail.com>
Co-authored-by: Armand Grillet <2117580+armandgrillet@users.noreply.github.com>

pkg/services/sqlstore/migrations/ualert/tables.go

@@ -260,6 +260,16 @@ func AddAlertRuleMigrations(mg *migrator.Migrator, defaultIntervalSeconds int64)
 			Default:  "1",
 		},
 	))
+
+	mg.AddMigration("add is_paused column to alert_rule table", migrator.NewAddColumnMigration(
+		alertRule,
+		&migrator.Column{
+			Name:     "is_paused",
+			Type:     migrator.DB_Bool,
+			Nullable: false,
+			Default:  "false",
+		},
+	))
 }
 
 func AddAlertRuleVersionMigrations(mg *migrator.Migrator) {
@@ -313,6 +323,16 @@ func AddAlertRuleVersionMigrations(mg *migrator.Migrator) {
 			Default:  "1",
 		},
 	))
+
+	mg.AddMigration("add is_paused column to alert_rule_versions table", migrator.NewAddColumnMigration(
+		alertRuleVersion,
+		&migrator.Column{
+			Name:     "is_paused",
+			Type:     migrator.DB_Bool,
+			Nullable: false,
+			Default:  "false",
+		},
+	))
 }
 
 func AddAlertmanagerConfigMigrations(mg *migrator.Migrator) {