chore: move the go code into a subfolder

apps/api/internal/notification/channels/error.go

@@ -0,0 +1,25 @@
+package channels
+
+import "errors"
+
+type CancelError struct {
+	Err error
+}
+
+func (e *CancelError) Error() string {
+	return e.Err.Error()
+}
+
+func NewCancelError(err error) error {
+	return &CancelError{
+		Err: err,
+	}
+}
+
+func (e *CancelError) Is(target error) bool {
+	return errors.As(target, &e)
+}
+
+func (e *CancelError) Unwrap() error {
+	return e.Err
+}