Alerting: Prevent updating rule uid matcher for silences (#88519)

Prevents updating the `__alert_rule_uid__` equality matcher (used for rule-specific silences) on existing silences

pkg/services/ngalert/models/testing.go

@@ -16,6 +16,7 @@ import (
 	"github.com/prometheus/common/model"
 	"github.com/stretchr/testify/require"
 
+	alertingModels "github.com/grafana/alerting/models"
 	"github.com/grafana/grafana/pkg/expr"
 	"github.com/grafana/grafana/pkg/services/datasources"
 	"github.com/grafana/grafana/pkg/services/folder"
@@ -1054,6 +1055,29 @@ func (n SilenceMutators) WithMatcher(name, value string, matchType labels.MatchT
 		s.Silence.Matchers = append(s.Silence.Matchers, &m)
 	}
 }
+func (n SilenceMutators) WithRuleUID(value string) Mutator[Silence] {
+	return func(s *Silence) {
+		name := alertingModels.RuleUIDLabel
+		m := amv2.Matcher{
+			Name:    &name,
+			Value:   &value,
+			IsRegex: util.Pointer(false),
+			IsEqual: util.Pointer(true),
+		}
+		for _, matcher := range s.Silence.Matchers {
+			if isRuleUIDMatcher(*matcher) {
+				*matcher = m
+				return
+			}
+		}
+		s.Silence.Matchers = append(s.Silence.Matchers, &m)
+	}
+}
+func (n SilenceMutators) Expired() Mutator[Silence] {
+	return func(s *Silence) {
+		s.EndsAt = util.Pointer(strfmt.DateTime(time.Now().Add(-time.Minute)))
+	}
+}
 
 func (n SilenceMutators) WithEmptyId() Mutator[Silence] {
 	return func(s *Silence) {