Allow head method httpendpoint (#1346)

* Allow for custom head method in HTTPEndpoint

Fix for #1221

* Fix formatting

* Allow custom head method in HTTPEndpoint

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

starlette/endpoints.py

@@ -23,7 +23,12 @@ def __await__(self) -> typing.Generator:
 
     async def dispatch(self) -> None:
         request = Request(self.scope, receive=self.receive)
-        handler_name = "get" if request.method == "HEAD" else request.method.lower()
+        handler_name = (
+            "get"
+            if request.method == "HEAD" and not hasattr(self, "head")
+            else request.method.lower()
+        )
+
         handler = getattr(self, handler_name, self.method_not_allowed)
         is_async = asyncio.iscoroutinefunction(handler)
         if is_async: