Update My Wallet to reflect change to self-managed wallet

[Alex Cornforth]

DEPENDS ON: #4

Now that we authenticate with self-managed wallets we're going to need to update the GreenstandWalletSDK.myWallet fucntion to account for this (or check if it is even still viable - we'll see what happens when we call it with our self-maanaged wallet handle).

Notes:

• Use the wallet api to help guide what we do here.

• This is unrelated to keycloak authentication in the AuthenticationService.swift file. You can ignore this file along with any of the authenticationService configuration parameters that are passed into the SDK.