Revert and fix Character player_name

Revert "Remove non-null constraint from Character player_name"

This reverts commit 69a86f8e0b6fa9c90eb2fea22afcc52a756791c8.

Revert "Fix population of new character fields"

This reverts commit b31571ae89d1918d511b95a39454bdca2c864626.

Populate Character player_name on creation