Protocol specification should define client UI standards for identity requests

[aaroncox]

The standard has:

1. Guidelines for how to implement generic signing requests: https://github.com/wharfkit/signing-request/blob/master/protocol-specification.md#implementation-guidelines
2. An appendix entry defining how identity requests work: https://github.com/wharfkit/signing-request/blob/master/protocol-specification.md#identity-requests

But there are no defined guidelines for how clients should implement identity requests. A future revision to the standard should include guidance on how to display identity requests, automatically attempting to select appropriate accounts, things to protect against, etc.

One thing missing from the Anchor implementation is showing which permission the request is made for.