Implement retry that automatically detect httpx and backoff (#119)

* server: implement retry that automatically detect httpx and backoff

Closes #118

* server: fix formatting

server/tests/test_retry_decorator.py

@@ -0,0 +1,55 @@
+import pytest
+import httpx
+from reflector.utils.retry import (
+    retry,
+    RetryTimeoutException,
+    RetryHTTPException,
+    RetryException,
+)
+
+
+@pytest.mark.asyncio
+async def test_retry_httpx(httpx_mock):
+    # this code should be force a retry
+    httpx_mock.add_response(status_code=500)
+    async with httpx.AsyncClient() as client:
+        with pytest.raises(RetryTimeoutException):
+            await retry(client.get)("https://test_url", retry_timeout=0.1)
+
+    # but if we add it in the retry_httpx_status_stop, it should not retry
+    async with httpx.AsyncClient() as client:
+        with pytest.raises(RetryHTTPException):
+            await retry(client.get)(
+                "https://test_url", retry_timeout=5, retry_httpx_status_stop=[500]
+            )
+
+
+@pytest.mark.asyncio
+async def test_retry_normal():
+    left = 3
+
+    async def retry_before_success():
+        nonlocal left
+        if left > 0:
+            left -= 1
+            raise Exception("test")
+        return True
+
+    result = await retry(retry_before_success)()
+    assert result is True
+    assert left == 0
+
+
+@pytest.mark.asyncio
+async def test_retry_max_attempts():
+    left = 3
+
+    async def retry_before_success():
+        nonlocal left
+        if left > 0:
+            left -= 1
+            raise Exception("test")
+        return True
+
+    with pytest.raises(RetryException):
+        await retry(retry_before_success)(retry_attempts=2)