Transport Return Route Protocol (RFC 0092)

[rolsonquadras]

Implement Transport Return Route Protocol in Aries Framework Go - https://github.com/hyperledger/aries-rfcs/tree/master/features/0092-transport-return-route.

[rolsonquadras]

Implementation of this protocol can be broken down into following issues:

1. Get access to sender verification key in Inbound transport (To store the transport based on verKey) - Inbound Transport handler - Access to Sender Verification Key #876
2. Support to configure framework with Transport return route option - To add values to the transport decorator.
3. Make the transport duplex - Use the stored transport based on the verKey of the recipient
   (sender in case of inbound) during outbound calls - DIDComm Transport(WS) - Support Duplex communication #877
4. BDD tests - Transport Return Route RFC - BDD Tests #893

[rolsonquadras]

Core framework support is implemented as part of PR #896.

Remaining issues for completing basic e2e implementation - #877 #893