Fix case-insensitive header redaction (#685)

* Normalize header redaction keys

Co-authored-by: astuyve <astuyve@gmail.com>

* feat: fmt

* less than 3.19.0

---------

Co-authored-by: datadog-official[bot] <214633350+datadog-official[bot]@users.noreply.github.com>
Co-authored-by: Rithika Narayan <rithika.narayan@datadoghq.com>

Author: 3 people

datadog_lambda/tag_object.py

@@ -62,6 +62,6 @@ def _should_try_string(obj):
 
 def _redact_val(k, v):
     split_key = k.split(".").pop() or k
-    if split_key in redactable_keys:
+    if split_key.lower() in redactable_keys:
         return "redacted"
     return v

tests/test_tag_object.py

@@ -73,13 +73,14 @@ def test_tag_object_max_depth_0(self):
             "vals": [{"thingOne": 1}, {"thingTwo": 2}],
         }
         spanMock = MagicMock()
+        expected_value = str(payload)
 
         tag_object(spanMock, "function.request", payload)
         spanMock.set_tag.assert_has_calls(
             [
                 call(
                     "function.request",
-                    "{'hello': 'world', 'level1': {'level2_dict': {'level3': 3}, 'level2_list': [None, True, 'nice', {'l3': 'v3'}], 'level2_bool': True, 'level2_int': 2}, 'vals': [{'thingOne': 1}, {'thingTwo': 2}]}",
+                    expected_value,
                 ),
             ],
             True,
@@ -105,6 +106,18 @@ def test_redacted_tag_object(self):
             True,
         )
 
+    def test_redacted_tag_object_case_insensitive(self):
+        payload = {
+            "Authorization": "secret",
+            "headers": {"X-AUTHORIZATION": "another"},
+        }
+        spanMock = MagicMock()
+        tag_object(spanMock, "function.request", payload)
+        spanMock.set_tag.assert_any_call("function.request.Authorization", "redacted")
+        spanMock.set_tag.assert_any_call(
+            "function.request.headers.X-AUTHORIZATION", "redacted"
+        )
+
     def test_json_tag_object(self):
         payload = {
             "token": "world",