Zanzana: Lazy load cached store info (#96452)

* Lazy load cached store infos

pkg/services/authz/zanzana/server/server.go

@@ -1,7 +1,6 @@
 package server
 
 import (
-	"errors"
 	"sync"
 
 	authzv1 "github.com/grafana/authlib/authz/proto/v1"
@@ -25,19 +24,16 @@ var _ authzextv1.AuthzExtentionServiceServer = (*Server)(nil)
 
 var tracer = otel.Tracer("github.com/grafana/grafana/pkg/services/authz/zanzana/server")
 
-var errStoreNotFound = errors.New("store not found")
-var errAuthorizationModelNotInitialized = errors.New("authorization model not initialized")
-
 type Server struct {
 	authzv1.UnimplementedAuthzServiceServer
 	authzextv1.UnimplementedAuthzExtentionServiceServer
 
 	openfga openfgav1.OpenFGAServiceServer
 
-	logger    log.Logger
-	modules   []transformer.ModuleFile
-	storeMap  map[string]storeInfo
-	storeLock *sync.Mutex
+	logger   log.Logger
+	modules  []transformer.ModuleFile
+	stores   map[string]storeInfo
+	storesMU *sync.Mutex
 }
 
 type storeInfo struct {
@@ -65,9 +61,9 @@ func NewAuthzServer(cfg *setting.Cfg, openfga openfgav1.OpenFGAServiceServer) (*
 
 func NewAuthz(openfga openfgav1.OpenFGAServiceServer, opts ...ServerOption) (*Server, error) {
 	s := &Server{
-		openfga:   openfga,
-		storeLock: &sync.Mutex{},
-		storeMap:  make(map[string]storeInfo),
+		openfga:  openfga,
+		storesMU: &sync.Mutex{},
+		stores:   make(map[string]storeInfo),
 	}
 
 	for _, o := range opts {