Code review comment for lp://qastaging/~afrantzis/mir/client-api-platform-operation-spike

> Couldn't the create function take the data and fds? Vis:

It could. However, neither data nor fds are required for a platform message, so I proposed this approach following the "constructor takes required arguments" rationale we used for the MirSurfaceSpec. The trade off is more functions vs having larger constructor calls with possibly null arguments and the potential to create immutable objects (if we choose not to have any other setters).

I don't have any strong preference for one approach over the other.