Migrate Seat Interface to the new approach

Hello,

I have problem to migrate seat into new approach. because many many class depend each other.

The most clean approach is to break template and make duplicate function, at end of migration process, we reintroduce template to reduce the amount of code.

This permit to adjust and test each class, before migrate all seat.

The second approach is to make all in one commit that contain all Seat and all her class. This is huge annd until we finish, we cannot compile to verify all is ok.

What do you think about that ? (and if you have another idea :) )