fix: IPFS gateway should return only json content

[wa0x6e]

🧿 Current issues / What's wrong ?

The /ipfs/* endpoint is currently returning json content.

But when the given CID is something else than a JSON file, the endpoint fail, with a timeout error (await response.json() is timing out)

💊 Fixes / Solution

• Return a 400 error when the content-type is not a json file

🚧 Changes

• reject the promise when the content-type is not matching a json content type
• reject the promise when parsing the body as json is failing.

🛠️ Tests

• Run the tests
• http://localhost:3000/ipfs/bafkreib5epjzumf3omr7rth5mtcsz4ugcoh3ut4d46hx5xhwm4b3pqr2vi should return a json content
• http://localhost:3000/ipfs/bafybeie2x4ptheqskiauhfz4w4pbq7o6742oupitganczhjanvffp2spti should return a 400 error

[bonustrack]

utACK