Easy re-authentication from within the game or launcher

When attempting to play Minecraft (Java Edition) after having logged in elsewhere, one is generally presented with an "Invalid session: Try restarting your game..." error. Ideally, the game would be able to re-authenticate itself without restarting (through the use of some game-launcher interface)*. This would likely be difficult for backwards compatibility and other reasons. If this is impossible, the launcher itself should be able to (a) detect that it has lost authentication lock (even just by polling every 30 seconds while the game is not running) and (b) offer the option to reconnect (probably with the notice that this will disconnect other sessions).

In general, the whole authentication process could do with a lot more transparency ("invalid session; restart your game" doesn't provide a whole lot of useful information about what's wrong or why the fix works) and I think some improvements might be due.

*One way this could be done is by simply setting a flag on versions that support in-game reconnection and having the launcher talk to the game via some API if the flag is present