Write test for Player::copyFrom

[BarthPaleologue]

The Player class is brittle for some parts and testing would help catching future bugs.

The most important is to test copyFrom and ensure that it indeeds perform a deep-copy.

By testing this method, adding new fields to Player without updating copyFrom would result in a test failure of the deep-copy.

[vr-varad]

hey @BarthPaleologue I would like to work on this issue would require some more info regarding the issue

[BarthPaleologue]

Welcome back :) I assigned you to the issue, let me know what you need to know to complete the issue!

Also don't forget about #245 haha as you are 95% there.