fix(payments): retry provider connect failures

tests/test_payment_http_client.py

@@ -1,6 +1,10 @@
 import unittest
 
-from bot.payment_providers.shared.http_client import HttpClientMixin
+from bot.payment_providers.shared.http_client import (
+    HttpClientMixin,
+    _PAYMENT_REQUEST_USER_AGENT,
+    _should_retry_transport_error,
+)
 
 
 class _DummyHttpClient(HttpClientMixin):
@@ -14,5 +18,15 @@ class PaymentHttpClientTests(unittest.IsolatedAsyncioTestCase):
         try:
             session = await client._get_session()
             self.assertTrue(session.connector.force_close)
+            self.assertTrue(session.trace_configs)
+            self.assertEqual(session.headers["User-Agent"], _PAYMENT_REQUEST_USER_AGENT)
         finally:
             await client.close()
+
+    async def test_http_client_retries_only_before_headers_are_sent(self):
+        self.assertTrue(
+            _should_retry_transport_error(TimeoutError(), {"headers_sent": False})
+        )
+        self.assertFalse(
+            _should_retry_transport_error(TimeoutError(), {"headers_sent": True})
+        )