Disabled caching for ActivityPub & WebFinger

ref https://linear.app/tryghost/issue/MOM-25

Whilst we're experimenting it's gonna be easier to not have to think about
caching affecting things. We'll disable it completely for now, and then decide
on a caching strategy that suits us down the line.

ghost/ghost/src/http/admin/controllers/activitypub.controller.ts

@@ -1,4 +1,4 @@
-import {Controller, Get, Param} from '@nestjs/common';
+import {Controller, Get, Header, Param} from '@nestjs/common';
 import {Roles} from '../../../common/decorators/permissions.decorator';
 import ObjectID from 'bson-objectid';
 import {JSONLDService} from '../../../core/activitypub/jsonld.service';
@@ -9,6 +9,7 @@ export class ActivityPubController {
         private readonly service: JSONLDService
     ) {}
 
+    @Header('Cache-Control', 'no-store')
     @Roles(['Anon'])
     @Get('actor/:id')
     async getActor(@Param('id') id: unknown) {
@@ -18,6 +19,7 @@ export class ActivityPubController {
         return this.service.getActor(ObjectID.createFromHexString(id));
     }
 
+    @Header('Cache-Control', 'no-store')
     @Roles(['Anon'])
     @Get('key/:owner')
     async getKey(@Param('owner') owner: unknown) {
@@ -27,6 +29,7 @@ export class ActivityPubController {
         return this.service.getPublicKey(ObjectID.createFromHexString(owner));
     }
 
+    @Header('Cache-Control', 'no-store')
     @Roles(['Anon'])
     @Get('outbox/:owner')
     async getOutbox(@Param('owner') owner: unknown) {

ghost/ghost/src/http/admin/controllers/webfinger.controller.ts

@@ -1,4 +1,4 @@
-import {Controller, Get, Query} from '@nestjs/common';
+import {Controller, Get, Header, Query} from '@nestjs/common';
 import {WebFingerService} from '../../../core/activitypub/webfinger.service';
 
 @Controller('.well-known/webfinger')
@@ -7,6 +7,7 @@ export class WebFingerController {
         private readonly service: WebFingerService
     ) {}
 
+    @Header('Cache-Control', 'no-store')
     @Get('')
     async getResource(@Query('resource') resource: unknown) {
         if (typeof resource !== 'string') {