Consider no_default_values_in_constructor: true for generated Scala sources

[arosien]

By default, ScalaPB generates default values for required fields, therefore making them optional to the user. This behavior can be disabled via:

import "scalapb/scalapb.proto";

option (scalapb.options) = {
  no_default_values_in_constructor: true;
};

[scholarsmate]

I think disabling default values in the constructor is a fine idea. Would you like to make the change?

[arosien]

TIL proto3 has no notion of a required field, so that is the reason why default values are generated for non-optional fields. (Yes, you can specify optional, which in Scala adds the Option wrapper to the field.)