SIP for Wallet client API draft

:loudspeaker:Please see original GH issue opened by @Kryan & Jannik based on some work Friedger has done in the past.
Draft in the comment just expand

This is a big utility unlock, :star2: please chime in particular:
1. wallet providers
2. builders

some TLDR and use cases:

Will need some testers to try out the UIUX in testnet soon.
Raise your hand if you are interested too.