fix: round-trip DAG-JSON and DAG-CBOR with embedded CIDs

DAG-JSON and DAG-CBOR can have embeded CIDs which are
deserialized to CID objects by the `@ipld/dag-json` and
`@ipld/dag-cbor` modules.

This fixes a bug whereby we were JSON.stringifying them
which lead to rubbish being returned from `.json()`.

packages/verified-fetch/src/verified-fetch.ts

@@ -128,7 +128,11 @@ export class VerifiedFetch {
       onProgress: options?.onProgress
     })
     options?.onProgress?.(new CustomProgressEvent<CIDDetail>('verified-fetch:request:end', { cid, path }))
-    const response = okResponse(JSON.stringify(result))
+    // return body as binary
+    const body = await this.helia.blockstore.get(cid)
+    const response = okResponse(body)
+    // return pre-parsed object with embedded CIDs as objects
+    response.json = async () => result
     response.headers.set('content-type', 'application/json')
     return response
   }
@@ -154,7 +158,11 @@ export class VerifiedFetch {
       onProgress: options?.onProgress
     })
     options?.onProgress?.(new CustomProgressEvent<CIDDetail>('verified-fetch:request:end', { cid, path }))
-    const response = okResponse(JSON.stringify(result))
+    // return body as binary
+    const body = await this.helia.blockstore.get(cid)
+    const response = okResponse(body)
+    // return pre-parsed object with embedded CIDs as objects
+    response.json = async () => result
     await this.setContentType(result, path, response)
     return response
   }

packages/verified-fetch/test/verified-fetch.spec.ts

@@ -224,6 +224,22 @@ describe('@helia/verifed-fetch', () => {
       await expect(resp.json()).to.eventually.deep.equal(obj)
     })
 
+    it('should return dag-json data with embedded CID', async () => {
+      const obj = {
+        hello: 'world',
+        link: CID.parse('QmNnooDu7bfjPFoTZYxMNLWUQJyrVwtbZg5gBMjTezGAJN')
+      }
+      const j = dagJson(helia)
+      const cid = await j.add(obj)
+
+      const resp = await verifiedFetch.fetch(cid)
+      const data = await resp.json()
+      expect(data).to.deep.equal({
+        hello: 'world',
+        link: CID.parse('QmNnooDu7bfjPFoTZYxMNLWUQJyrVwtbZg5gBMjTezGAJN')
+      })
+    })
+
     it('should handle dag-cbor block', async () => {
       const obj = {
         hello: 'world'
@@ -238,6 +254,22 @@ describe('@helia/verifed-fetch', () => {
       await expect(resp.json()).to.eventually.deep.equal(obj)
     })
 
+    it('should return dag-cbor data with embedded CID', async () => {
+      const obj = {
+        hello: 'world',
+        link: CID.parse('QmNnooDu7bfjPFoTZYxMNLWUQJyrVwtbZg5gBMjTezGAJN')
+      }
+      const j = json(helia)
+      const cid = await j.add(obj)
+
+      const resp = await verifiedFetch.fetch(cid)
+      const data = await resp.json()
+      expect(data).to.deep.equal({
+        hello: 'world',
+        link: CID.parse('QmNnooDu7bfjPFoTZYxMNLWUQJyrVwtbZg5gBMjTezGAJN')
+      })
+    })
+
     it('should handle json block', async () => {
       const obj = {
         hello: 'world'