chore: accept Mapping as well as SupportsDuplicateItems

Although our types.SupportsDuplicateItems type is wider than Dict and
Mapping, it's not a familar type to users, so explicitly accepting
Mapping in the from_http() functions should make it more clear to users
that a dict-like object is required for the headers argument.

Signed-off-by: Hal Blackburn <hwtb2@cam.ac.uk>

cloudevents/conversion.py

@@ -91,7 +91,9 @@ def from_json(
 
 def from_http(
     event_type: typing.Type[AnyCloudEvent],
-    headers: types.SupportsDuplicateItems[str, str],
+    headers: typing.Union[
+        typing.Mapping[str, str], types.SupportsDuplicateItems[str, str]
+    ],
     data: typing.Optional[typing.Union[str, bytes]],
     data_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
 ) -> AnyCloudEvent:

cloudevents/http/conversion.py

@@ -37,7 +37,9 @@ def from_json(
 
 
 def from_http(
-    headers: types.SupportsDuplicateItems[str, str],
+    headers: typing.Union[
+        typing.Mapping[str, str], types.SupportsDuplicateItems[str, str]
+    ],
     data: typing.Optional[typing.Union[str, bytes]],
     data_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
 ) -> CloudEvent:

cloudevents/pydantic/v1/conversion.py

@@ -21,7 +21,9 @@ from cloudevents.sdk import types
 
 
 def from_http(
-    headers: types.SupportsDuplicateItems[str, str],
+    headers: typing.Union[
+        typing.Mapping[str, str], types.SupportsDuplicateItems[str, str]
+    ],
     data: typing.Optional[typing.AnyStr],
     data_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
 ) -> CloudEvent:

cloudevents/pydantic/v2/conversion.py

@@ -22,7 +22,9 @@ from cloudevents.sdk import types
 
 
 def from_http(
-    headers: types.SupportsDuplicateItems[str, str],
+    headers: typing.Union[
+        typing.Mapping[str, str], types.SupportsDuplicateItems[str, str]
+    ],
     data: typing.Optional[typing.AnyStr],
     data_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
 ) -> CloudEvent: