Alerting: Ensure case-sensitive ordering for alert rule group column

The query which fetches alert rules in a paginated manner ordered by `rule_group` can result in strange and inconsistent ordering when the database uses a case-insensitive collation for the `rule_group` column. This can lead to scenarios where rules from different groups are interleaved in the results, making pagination unreliable and the returned number of rule_groups incorrect.

Related to #88990

pkg/services/sqlstore/migrations/migrations.go

@@ -156,4 +156,6 @@ func (oss *OSSMigrations) AddMigration(mg *Migrator) {
 	ualert.DropTitleUniqueIndexMigration(mg)
 
 	ualert.AddStateFiredAtColumn(mg)
+
+	ualert.CollateAlertRuleGroup(mg)
 }

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

@@ -0,0 +1,9 @@
+package ualert
+
+import "github.com/grafana/grafana/pkg/services/sqlstore/migrator"
+
+// CollateAlertRuleGroup ensures that rule_group column collates.
+func CollateAlertRuleGroup(mg *migrator.Migrator) {
+	mg.AddMigration("ensure rule_group column is case sensitive in returned results", migrator.NewRawSQLMigration("").
+		Mysql("ALTER TABLE alert_rule MODIFY rule_group VARCHAR(190) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_as_cs NOT NULL;"))
+}