Pythonize input_type name in py_input_message (#436)

Co-authored-by: konstantin <konstantin.klein@hochfrequenz.de>
Co-authored-by: James Hilton-Balfe <gobot1234yt@gmail.com>
Fixes https://github.com/danielgtaylor/python-betterproto/issues/427
Fixes https://github.com/danielgtaylor/python-betterproto/issues/438

src/betterproto/plugin/models.py

@@ -750,7 +750,7 @@ class ServiceMethodCompiler(ProtoContentBase):
         # comparable with method.input_type
         for msg in self.request.all_messages:
             if (
-                msg.py_name == name.replace(".", "")
+                msg.py_name == pythonize_class_name(name.replace(".", ""))
                 and msg.output_file.package == package
             ):
                 return msg