feat: impl bearer auth middleware

apps/backend/internal/user/err.go

@@ -0,0 +1,19 @@
+package user
+
+import (
+	"fmt"
+
+	"github.com/google/uuid"
+)
+
+type NotFoundError struct {
+	id uuid.UUID
+}
+
+func newNotFoundError(id uuid.UUID) *NotFoundError {
+	return &NotFoundError{id}
+}
+
+func (e *NotFoundError) Error() string {
+	return fmt.Sprintf("user not found: %v", e.id)
+}