Verifying transactions

[Gozala]

Goal

Every write to the memory space is signed and verified by the space. Writes with invalid authorization are rejected. Reads also require authorization and are verified.

Deliverable

• common-memory starts rejecting unauthorized transactions, that is either not signed or signed by an unauthorized issuer.
• common-memory starts rejecting unauthorized watch and query requests

⚠️ Here we do not yet support delegated authorizations.

Dependencies

• Signed transactions #333

[Gozala]

In progress via #433