FR: app permissions to access wallet data

[Maxnflaxl]

Feature title
app permissions to access wallet data

Describe the current situation we have
Right now, by default, apps are allowed to query the blockchain info. They can also create txs, but each tx should be approved by the user.

Describe the solution you'd like
We can add a method for app shaders to discover user balance, kind of like with MetaMask where you have to sign a message to allow the DApp to see your balance and suggest transactions.
Apps with enough privilege level (i.e. approved by the user) will be able to call it and use it to compute the amounts for components such as the (25%, 50%, 75%, ‘MAX’) amount button.

Describe alternatives you've considered (if relevant)
A clear and concise description of any alternative solutions or features you've considered.

Additional context
The problem with this is that DApps that are not ran locally inside the wallet, but hosted on a server(like BeamAssets), could map your wallet holdings to your IP.
Of course by default apps won’t be able to query user balance, unless user explicitly allows.