Feature: Directory upload with IPFS service

[MHHukiewitz]

In response to aleph-im/aleph-client#187.

Useful resources:

• Only POST /api/v0/ipfs/add_file exists so far: https://github.com/aleph-im/pyaleph/blob/master/src/aleph/web/controllers/ipfs.py
• Which uses the IPFS service in a limited extent: https://github.com/aleph-im/pyaleph/blob/master/src/aleph/services/ipfs/service.py
• Which needs to be updated to correctly add directories as multipart requests to IPFS kubo: https://docs.ipfs.tech/reference/kubo/rpc/#api-v0-add

If possible:

• Make POST /api/v0/ipfs/add_file also accept directories, similar to the Kubo RPC method

Follow up:

• Adjust https://github.com/aleph-im/aleph-sdk-python and https://github.com/aleph-im/aleph-client to allow directories, too.