Enable storage of records with other authors/recipients without clobbering authorship/recipient attribution

[csuwildcat]

No description provided.

[diehuxx]

Writing down our thoughts from our chat this afternoon:

What use case does this solve?

It allows a given protocol context tree to be shared between multiple DWNs.

Example

If Alice and Bob have a context tree of records with some contextId, they may want to invite Carol into the fold. Carol needs to establish a protocol context with the same contextId that Alice and Bob have, meaning she needs the exact same root RecordsWrite message that Alice and Bob have.

But how will Carol's DWN accept such a message if Alice/Bob pass her the exact message that they have? Alice signed the message as author, but Carol's protocol definition doesn't necessarily say "allow anyone to write a root record". I suppose Carol could create a PermissionsGrant to accept the root RecordsWrite, but that's heavy-handed. We can do better.

So we propose this flow:

1. Alice sends a RecordsWrite to Bob
2. Bob sends the RecordsWrite to Carol
3. Carol adds her own signature to the authorization. Now Alice's signature is in the author JWS, and Carol's signature is in the owner JWS.
4. Carol passes this updated RecordsWrite to her DWN, which sees that owner === tenant and accepts the message.

How does Carol decide whether she wants to add a signature and pass it to her DWN? We leave that to the application level.

[csuwildcat]

@thehenrytsai has a PR out for this as of today.