Use single certificate for delegation + registration

[mesudip]

Why

• To make delegation transaction a little smaller
• Stake registration certificate (0) is deprecated in conway era

What

When Stake Address is not registered, We are currently creating transaction with 2 certificates (registration, delegation). But this can be done in single certificate in conway era. Furthermore, the used certificate-type (0) is deprecated.

How

Example (cert list in decoded-tx) (Current implementation)

[
    [
        0, // stake-registration cert ; Deprecated in Conway Era
        [
            0, "992D25F1234F161763F5FAAEEA857BAF06DE242547BDE90895019CDE"
        ]
    ],
    [
        9, // vote_deleg_cert
        [
            0, "992D25F1234F161763F5FAAEEA857BAF06DE242547BDE90895019CDE"
        ],
        [
            0, "001021A9B538F693F5293B9AD77E9FD2FEBE5ECD66CF8BB2844B4A8D"
        ]
    ]
]

Suggested change (certs in decoded tx)

[
    [
        12, // vote_reg_deleg_cert
        [
            0, "992D25F1234F161763F5FAAEEA857BAF06DE242547BDE90895019CDE"
        ],
        [
            0, "001021A9B538F693F5293B9AD77E9FD2FEBE5ECD66CF8BB2844B4A8D"
        ],
        2000000 // deposit amount
    ]
]

NB Refer to corresponding certificate builder in cardano-serialization-lib to create the registration_delegation_cert

[Ryun1]

@mesudip

I agree with the motivation and rationale here - great catch!
But unfortunately hardware wallets have not supported these "combination" certificates (see CIP-21 Certificates)
So by using them we could break the user flow for HWWs

Stake registration certificate (0) is deprecated in conway era

*depreciated in the era after conway
Maybe we should just move to use the new Conway reg_cert?

[Ryun1]

we can close for now