Use IPFS to store files in aepp-aexistence

[emil-apeunit]

Target

Use IPFS to store files

Current State

Currently if a user chooses to upload an image we send the image
to our api and store the image on our server. The filename then is the sha256
hash of the file.

What we want

Store the file on an ipfs node instead

What to do

• When a user inputs a file send it from frontend to an IPFS node directly
  • Do we need to set up an IPFS node or can we use infura for example?
  • The displayed image in the chat bubble must either come from ipfs or from
    the file stored in frontend
• The returned IPFS Hash needs to be stored in frontend to be later sent to the
  contract
• The usual flow continues where the user inputs a comment
• When the notarize method on the contract is called we need to send an
  additional parameter with the ipfsHash
  • This is needed to be able to display the image later
• The Proof-Contract is already altered to take the ipfHash argument
• The Pages to display the list of proofs or a single proof must now read the
  ipfs hash from the contract and display the image accordingly

[ShamariFeaster]

I've created a pull request that addresses this. Please review