Implement an `IpfsFileUploader` in the aggregator

[jpraynaud]

Why

The aggregator must publish the immutable archives to IPFS and expose their CIDs (under their directory CID umbrella) so that clients can download them through IPFS.

What

Implement an IpfsFileUploader in the aggregator that publishes compressed immutable archives to a local IPFS node and references their directory CID.

How

• Implement the IpfsFileUploader (implements ImmutableFilesUploader trait):
  • Connect the uploader to a local IPFS node
  • Add the compressed immutable archive to the published IPFS directory
  • Retrieve the CID of the published directory
  • Reference the directory CID in the URI template in the artifact