redirect webfinger of domain to instance actor

(Johann150 yells at cloud)

packages/backend/src/server/well-known.ts

@@ -101,12 +101,22 @@ router.get(webFingerPath, async ctx => {
 			isSuspended: false,
 		} : 422;
 
-	if (typeof ctx.query.resource !== 'string') {
+	let resource = ctx.query.resource;
+
+	if (typeof resource !== 'string') {
 		ctx.status = 400;
 		return;
 	}
 
-	const query = generateQuery(ctx.query.resource.toLowerCase());
+	resource = resource.toLowerCase();
+
+	// Mastodon sometimes only checks for the domain name,
+	// which should be rewritten to the instance actor.
+	if (`https://${config.host}`.toLowerCase() === resource) {
+		resource = `acct:instance.actor@${config.host}`;
+	}
+
+	const query = generateQuery(resource);
 
 	if (typeof query === 'number') {
 		ctx.status = query;