Add helper to get the attachedType resource

Since it's likely that listeners will need to base logic off this,
it makes sense to provide this for them and only do it once.

Author: CarsonF

src/components/file/media/events/can-update-event.ts

@@ -1,5 +1,7 @@
-import { Injectable, Optional, Scope } from '@nestjs/common';
+import { Inject, Injectable, Optional, Scope } from '@nestjs/common';
+import { CachedByArg as Once } from '@seedcompany/common';
 import { PollVoter } from '~/common';
+import { ResourceResolver, ResourcesHost } from '~/core';
 import { AnyMedia, MediaUserMetadata } from '../media.dto';
 
 /**
@@ -8,9 +10,20 @@ import { AnyMedia, MediaUserMetadata } from '../media.dto';
  */
 @Injectable({ scope: Scope.TRANSIENT })
 export class CanUpdateMediaUserMetadataEvent {
+  @Inject() private readonly resourceHost: ResourcesHost;
+  @Inject() private readonly resourceResolver: ResourceResolver;
+
   constructor(
     @Optional() readonly media: AnyMedia,
     @Optional() readonly input: MediaUserMetadata,
     @Optional() readonly allowUpdate: PollVoter<boolean>,
   ) {}
+
+  @Once() async getAttachedResource() {
+    const attachedResName = this.resourceResolver.resolveTypeByBaseNode(
+      this.media.attachedTo[0],
+    );
+    const attachedResource = await this.resourceHost.getByName(attachedResName);
+    return attachedResource;
+  }
 }