Crafatar no longer supports lookup by username

[pandapaul]

We use crafatar to grab avatars by username, but due to a Mojang API change they're no longer supporting lookup by username. We don't store user UUIDs, so we can use Mojang's API to convert username to UUID then fetch avatar by UUID.

We should, however, consider migrating the whole service to use user UUID instead of username. Usernames already have been problematic in the UI due to their flexibility. Since usernames can be changed, a player would lose their progress with minecraftdailies.com in doing so.

[Wing01]

Put in a temp fix that will render avatars based on username again. Will circle back to UUID support at some point