fix: synchronize DWH registry snapshots

tools/dwh-auth/internal/securefile/securefile_linux.go

@@ -291,6 +291,16 @@ func (d *Dir) Names() ([]string, error) {
 // Lock opens or creates a protected 0600 lock file and acquires an exclusive
 // advisory lock. Close releases the lock and descriptor.
 func (d *Dir) Lock(name string) (*Lock, error) {
+	return d.lock(name, syscall.LOCK_EX)
+}
+
+// LockShared opens or creates a protected 0600 lock file and acquires a shared
+// advisory lock. Close releases the lock and descriptor.
+func (d *Dir) LockShared(name string) (*Lock, error) {
+	return d.lock(name, syscall.LOCK_SH)
+}
+
+func (d *Dir) lock(name string, lockMode int) (*Lock, error) {
 	if err := validName(name); err != nil {
 		return nil, err
 	}
@@ -327,7 +337,7 @@ func (d *Dir) Lock(name string) (*Lock, error) {
 			_ = syscall.Close(fd)
 			return nil, err
 		}
-		if err := syscall.Flock(fd, syscall.LOCK_EX); err != nil {
+		if err := syscall.Flock(fd, lockMode); err != nil {
 			_ = syscall.Close(fd)
 			return nil, err
 		}