Operations: Add operation for Shared Storage (IPFS) uploads, and move API calls to batch worker

[peterbroadhurst]

[awrichar]

I took an initial look at this, and found one blocker to moving the IPFS upload into batch dispatch.

The steps for a broadcast are:

1. Message persistence (broadcast manager)
2. Batch assembly (batch manager)
3. Batch persistence (batch manager)
4. Batch dispatch (broadcast manager)

Currently the IPFS blob publish happens in 1, and the IPFS reference is added to the data item. This then gets incorporated and hashed as part of the batch payload in 3, at which point the payload is considered immutable.

If we move the IPFS blob publish to 4 (which is where the blob transfer happens already in the case of private messages), there is no way to record the IPFS reference without altering the batch payload.

The two routes forward that I can see:

• Add an additional hook between 2 and 3, and perform the IPFS publish there
• Restructure how the batch payload and hash are recorded, so that the the IPFS publish can happen in 4 without invalidating the batch

I'd lean toward the latter if possible, although this needs some discussion and may tie into the batch payload changes in #506.

[awrichar]

Part of this work is now accomplished in #596