[Feature Request] Support updating player skins on Paper servers

[DaniDipp]

Problem

When using Player#setPlayerProfile() from the Paper API to update player's skins on the fly, the player's icon in BTLP's tablist is not updated to reflect their new skin. This is due to the bungee server not being notified of this update. This is a problem because the visual desync significantly reduces the usability of the tab list as a means to identify players.

Steps to recreate

1. Set up Paper server behind Bungee proxy.
2. Install BungeeTablistPlus & BTLPBukkitBridge
3. Set up plugin to edit player profile skin via Player#setPlayerProfile()

Here is a snippet for it:

var profile = player.getPlayerProfile();
var textures = profile.getTextures();

try {
    var url = new URL("http://textures.minecraft.net/texture/2cbf0187c3058829e3b10706bad8e77a74b522666cb7e85d838f16e30d642065");
    textures.setSkin(url, SkinModel.CLASSIC);
} catch (MalformedURLException e) {
    throw new IllegalStateException(e);
}

profile.setTextures(textures);
player.setPlayerProfile(profile);

I also put my experimentation code and .jar on GitHub: DaniDipp/MinimalSkinUpdater

4. Notice that the player icon in the BTLP tablist doesn't change when your skin does.

Proposed solution

• Use BukkitBridge to send player data to BTLP, if available.

Other observations:

• The CMI tablist shows the new skin correctly, AdvancedTabOverlay currently doesn't
• CMI tablist:
  
• BTLP tablist:
  

[DaniDipp]

See #754

[DaniDipp]

I just learned that for the skin and tablist icon to be visible to other players, it has to have a valid signature which can only be obtained by properly updating a player's skin through Mojang (or via the MineSkin api)