/spawn command configuration

CMDBOOK-2295 - Reported by Amicus.Minecraft

Can the /spawn command be configured to send a player to one spawn point regardless of which world they are in?

Say I have the following worlds:
# WORLD
# WORLD_NETHER
# CREATIVE
# GASBOMBS

If a player uses /spawn in GASBOMBS, I want them to be teleported to the spawn point of WORLD, *not* the spawn point of GASBOMBS.

In the configuration file, this option could have two settings.

$ spawn-locations:
$ exact-spawn: false
$ main-world: WORLD
$ multiworld-spawn: false

Set "multiworld-spawn" to "true" to enable the current system of each world having its own spawn. Set it to "false" to have all '/spawn' command executions send the player to the main world's spawn.

The issue names no files or tests. Start by locating the /spawn command and its configuration handling, then trace how world-specific spawn selection works. Done means the configuration can select either each world's spawn or the main world's spawn for every /spawn execution, with coverage for both settings.

Written by the indexing model from the issue text.