Merge commit from fork

* fix(backend): Fix an issue where the origin of ActivityPub lookup response was not validated correctly.

[GHSA-6w2c-vf6f-xf26](https://github.com/misskey-dev/misskey/security/advisories/GHSA-6w2c-vf6f-xf26)

Signed-off-by: eternal-flame-AD <yume@yumechi.jp>

* Enhance: Add configuration option to disable all external redirects when responding to an ActivityPub lookup (config.disallowExternalApRedirect)

Signed-off-by: eternal-flame-AD <yume@yumechi.jp>

* fixup! fix(backend): Fix an issue where the origin of ActivityPub lookup response was not validated correctly.

* docs & one edge case

Signed-off-by: eternal-flame-AD <yume@yumechi.jp>

* apply suggestions

Signed-off-by: eternal-flame-AD <yume@yumechi.jp>

* remove stale frontend reference to _responseInvalidIdHostNotMatch

Signed-off-by: eternal-flame-AD <yume@yumechi.jp>

* apply suggestions

Signed-off-by: eternal-flame-AD <yume@yumechi.jp>

---------

Signed-off-by: eternal-flame-AD <yume@yumechi.jp>

packages/backend/src/config.ts

@@ -73,6 +73,7 @@ type Source = {
 	proxyBypassHosts?: string[];
 
 	allowedPrivateNetworks?: string[];
+	disallowExternalApRedirect?: boolean;
 
 	maxFileSize?: number;
 
@@ -149,6 +150,7 @@ export type Config = {
 	proxySmtp: string | undefined;
 	proxyBypassHosts: string[] | undefined;
 	allowedPrivateNetworks: string[] | undefined;
+	disallowExternalApRedirect: boolean;
 	maxFileSize: number;
 	clusterLimit: number | undefined;
 	id: string;
@@ -287,6 +289,7 @@ export function loadConfig(): Config {
 		proxySmtp: config.proxySmtp,
 		proxyBypassHosts: config.proxyBypassHosts,
 		allowedPrivateNetworks: config.allowedPrivateNetworks,
+		disallowExternalApRedirect: config.disallowExternalApRedirect ?? false,
 		maxFileSize: config.maxFileSize ?? 262144000,
 		clusterLimit: config.clusterLimit,
 		outgoingAddress: config.outgoingAddress,