Migrates SSinstancing to Redis from world.Export() (#17679)

code/modules/server_commands/servermsg.dm

@@ -0,0 +1,38 @@
+/**
+  * # Server Command
+  *
+  * Datum to handle both sending and receiving of server commands
+  *
+  * This datum is an extension of the redis callback and is designed for tighter integration with the BYOND servers.
+  * This list is registered and managed by SSintancing, not SSredis.
+  * NOTE: These commands are "fire and forget". If you need specific data from each server, use world/Topic still
+  */
+/datum/server_command
+	/// Does the sending server want to ignore this command? This is almost always yes unless you are doing testing stuff
+	var/ignoreself = TRUE
+	/// The source BYOND server for this message
+	var/source = null
+	/// The command name (must be unique)
+	var/command_name = null
+	/// Associative list of command args
+	var/list/command_args = list()
+
+/datum/server_command/proc/execute(source, command_args)
+	CRASH("execute(source, command_args) not overriden for [type]!")
+
+/datum/server_command/proc/dispatch(command_args)
+	SHOULD_NOT_OVERRIDE(TRUE) // No messing with
+
+	// Aight get serializing
+	var/list/serializeable_data = list()
+	serializeable_data["src"] = GLOB.configuration.system.instance_id
+	serializeable_data["cmd"] = command_name
+	serializeable_data["args"] = command_args
+
+	var/payload = json_encode(serializeable_data)
+
+	SSredis.publish(SERVER_MESSAGES_REDIS_CHANNEL, payload)
+
+// Override this if you want a cleaner method for putting together dispatch args
+/datum/server_command/proc/custom_dispatch()
+	CRASH("custom_dispatch() not overriden for [type]!")