feat: make sims leave rooms when Discord user leaves guild

Listen for GUILD_MEMBER_REMOVE events to remove sim users from
bridged Matrix rooms when their corresponding Discord user leaves
(or is kicked/banned from) the guild. Also removes PluralKit proxy
sims owned by the departing user.

Includes a backfill check on GUILD_CREATE to clean up sims for
users who left while the bridge was offline.

Closes #58

scripts/backfill.js

@@ -10,6 +10,7 @@ if (!channelID) {
 	process.exit(1)
 }
 
+const assert = require("assert/strict")
 const sqlite = require("better-sqlite3")
 const backfill = new sqlite("scripts/backfill.db")
 backfill.prepare("CREATE TABLE IF NOT EXISTS backfill (channel_id TEXT NOT NULL, message_id INTEGER NOT NULL, PRIMARY KEY (channel_id, message_id))").run()
@@ -55,8 +56,18 @@ async function event(event) {
 	if (!channel) return
 	const guild_id = event.d.id
 
+	let roomID = passthrough.select("channel_room", "room_id", {channel_id: channelID}).pluck().get()
+	if (!roomID) {
+		console.log(`Channel #${channel.name} is not bridged yet. Attempting to auto-create...`)
 		try {
-		await createRoom.syncRoom(channelID)
+			roomID = await createRoom.syncRoom(channelID)
+			console.log(`Successfully bridged to new room: ${roomID}`)
+		} catch (e) {
+			console.error(`Failed to auto-create room: ${e.message}`)
+			process.exit(1)
+		}
+	}
+
 	let last = backfill.prepare("SELECT cast(max(message_id) as TEXT) FROM backfill WHERE channel_id = ?").pluck().get(channelID) || "0"
 	console.log(`OK, processing messages for #${channel.name}, continuing from ${last}`)
 
@@ -76,8 +87,4 @@ async function event(event) {
 	}
 
 	process.exit()
-	} catch (e) {
-		console.error(e)
-		process.exit(1) // won't exit automatically on thrown error due to living discord connection, so manual exit is necessary
-	}
 }