rpc: votegov: Add support for owner and operator address

[DocteurPing]

Summary

Enables support for address support on votegov to vote with an address in addition to the currently accepted masternode ID.

How

• Over the wire, TX still uses masternode ID.
• The RPC API now auto selects the masternode ID based on the address provided.
• The selection order:
  • MasternodeID
  • OwnerAdress
  • OperatorAddress

Limitations

• Throws an error when there is no reasonable choice available (invalid address/masternodeId, address does not own/operate a masternode).

[Bushstar]

Note that you only need as uint256 will default initialise itself as the class has a default constructor.

uint256 mnId;

[Bushstar]

Address can be 26-35 chars long for P2PKH and 42 for P2WPKH. I'd work on getting the correct mnId before calling GetMasternode.

[Bushstar]

You need to call IsValidDestination on dest to make sure it is valid. You can do this in the else statement.

        if (id.length() == 64) {
            mnId = ParseHashV(id, "masternodeId");
        } else {
            CTxDestination dest = DecodeDestination(id);
            if (!IsValidDestination(dest)) {
                throw JSONRPCError(RPC_INVALID_PARAMETER,
                                    strprintf("The masternode id or address is not valid: %s", id));
            }
            // Call GetMasternodeIdByOwner and GetMasternodeIdByOperator here.
        }

[Bushstar]

Check that masterNodeIdByOperator is valid or you will get a std::bad_optional_access thrown on masterNodeIdByOperator.value(). I'd structure it like the following:

if (auto masterNodeIdByOwner = view.GetMasternodeIdByOwner(ckeyId)) {
    mnId = masterNodeIdByOwner.value();
} else if (auto masterNodeIdByOperator = view.GetMasternodeIdByOperator(ckeyId)) {
    mnId = masterNodeIdByOperator.value();
}

[Bushstar]

We need to make sure that the provided address is either P2PKH or a P2WPKH, otherwise if someone passes a different variant then std::get will throw a std::bad_variant_access.

            const CKeyID ckeyId  = dest.index() == PKHashType ? CKeyID(std::get<PKHash>(dest))
                                 : dest.index() == WitV0KeyHashType ? CKeyID(std::get<WitnessV0KeyHash>(dest))
                                 : CKeyID();

[shohamc1]

A bit too hard to read IMO, better to break it down into ifs.