Alerting: Verify receiver permission read on rule create/update (#94286)

* Alerting: Verify receiver permission read on rule create/update

pkg/services/ngalert/models/receivers.go

@@ -2,6 +2,7 @@ package models
 
 import (
 	"context"
+	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -559,6 +560,10 @@ func (r *Receiver) GetUID() string {
 	return r.UID
 }
 
+func NameToUid(name string) string {
+	return base64.RawURLEncoding.EncodeToString([]byte(name))
+}
+
 func (r *Receiver) Fingerprint() string {
 	sum := newFingerprint()