Add signature providers

Requires: common-ci-configuration!75 (merged)

python/tests/proto-protocol/test_proto_to_legacy_api.py

@@ -44,5 +44,5 @@ def test_op_proto_to_legacy_api():
         b'var.is_object()\n'
         b'cpp_proto_to_legacy_api requires JSON object as an argument\n'
         b'    {}\n'
-        b'    protobuf_protocol_impl.inl:625 operator()'
+        b'    protobuf_protocol_impl.inl:627 operator()'
     )