Added initial support for Outbox to Actors

ref https://linear.app/tryghost/issue/MOM-32

This adds the basic building blocks for an Outbox for an Actor, currently it's
hardcoded - which'll let us at lest test integration with other platforms.

JSONLDService is an awful name, but it's late and this is a prototype.

ghost/ghost/src/core/activitypub/jsonld.service.ts

@@ -0,0 +1,51 @@
+import {Inject} from '@nestjs/common';
+import {ActorRepository} from './actor.repository';
+import ObjectID from 'bson-objectid';
+
+export class JSONLDService {
+    constructor(
+        @Inject('ActorRepository') private repository: ActorRepository,
+        @Inject('ActivityPubBaseURL') private url: URL
+    ) {}
+
+    async getActor(id: ObjectID) {
+        const actor = await this.repository.getOne(id);
+        return actor?.getJSONLD(this.url);
+    }
+
+    async getPublicKey(owner: ObjectID) {
+        const actor = await this.repository.getOne(owner);
+        return actor?.getJSONLD(this.url).publicKey;
+    }
+
+    async getOutbox(owner: ObjectID) {
+        const actor = await this.repository.getOne(owner);
+        if (!actor) {
+            return null;
+        }
+        const json = actor.getJSONLD(this.url);
+        return {
+            '@context': 'https://www.w3.org/ns/activitystreams',
+            id: json.outbox,
+            summary: `Outbox for ${actor.username}`,
+            type: 'OrderedCollection',
+            totalItems: 1,
+            orderedItems: [{
+                type: 'Create',
+                actor: json.id,
+                to: [
+                    'https://www.w3.org/ns/activitystreams#Public'
+                ],
+                object: {
+                    type: 'Note',
+                    name: 'My First Note',
+                    content: '<p>Hello, world!</p>',
+                    attributedTo: json.id,
+                    to: [
+                        'https://www.w3.org/ns/activitystreams#Public'
+                    ]
+                }
+            }]
+        };
+    }
+}

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

@@ -0,0 +1,38 @@
+import {Controller, Get, Query} from '@nestjs/common';
+import {Roles} from '../../../common/decorators/permissions.decorator';
+import ObjectID from 'bson-objectid';
+import {JSONLDService} from '../../../core/activitypub/jsonld.service';
+
+@Controller('activitypub')
+export class ActivityPubController {
+    constructor(
+        private readonly service: JSONLDService
+    ) {}
+
+    @Roles(['Anon'])
+    @Get('actor')
+    async getActor(@Query('id') id: unknown) {
+        if (typeof id !== 'string') {
+            throw new Error('Bad Request');
+        }
+        return this.service.getActor(ObjectID.createFromHexString(id));
+    }
+
+    @Roles(['Anon'])
+    @Get('key')
+    async getKey(@Query('owner') owner: unknown) {
+        if (typeof owner !== 'string') {
+            throw new Error('Bad Request');
+        }
+        return this.service.getPublicKey(ObjectID.createFromHexString(owner));
+    }
+
+    @Roles(['Anon'])
+    @Get('outbox')
+    async getOutbox(@Query('owner') owner: unknown) {
+        if (typeof owner !== 'string') {
+            throw new Error('Bad Request');
+        }
+        return this.service.getOutbox(ObjectID.createFromHexString(owner));
+    }
+}

ghost/ghost/src/nestjs/modules/admin-api.module.ts

@@ -3,13 +3,15 @@ import {ExampleController} from '../../http/admin/controllers/example.controller
 import {ExampleService} from '../../core/example/example.service';
 import {ExampleRepositoryInMemory} from '../../db/in-memory/example.repository.in-memory';
 import {ActorRepositoryInMemory} from '../../db/in-memory/actor.repository.in-memory';
+import {ActivityPubController} from '../../http/admin/controllers/activitypub.controller';
 import {WebFingerService} from '../../core/activitypub/webfinger.service';
+import {JSONLDService} from '../../core/activitypub/jsonld.service';
 
 class AdminAPIModuleClass {}
 
 export const AdminAPIModule: DynamicModule = {
     module: AdminAPIModuleClass,
-    controllers: [ExampleController],
+    controllers: [ExampleController, ActivityPubController],
     exports: [ExampleService, 'WebFingerService'],
     providers: [
         ExampleService,
@@ -22,6 +24,7 @@ export const AdminAPIModule: DynamicModule = {
         }, {
             provide: 'WebFingerService',
             useClass: WebFingerService
-        }
+        },
+        JSONLDService
     ]
 };