feat(zarinhub): implement card to iban client

backend/internal/zarinhub/errors.go

@@ -0,0 +1,11 @@
+package zarinhub
+
+import "errors"
+
+var (
+	ErrAuthentication  = errors.New("zarinhub authentication failed")
+	ErrTimeout         = errors.New("zarinhub request timed out")
+	ErrUnavailable     = errors.New("zarinhub service unavailable")
+	ErrRejected        = errors.New("zarinhub rejected request")
+	ErrInvalidResponse = errors.New("zarinhub returned invalid response")
+)