Credential/Presentation verify fails if serde_json feature arbitrary_precision is enabled.

[vdods]

I'm currently digging into the precise cause, but it seems like the something in Credential/Presentation's impl of to_dataset_for_signing is not correctly forming the dataset when this arbitrary_precision feature is enabled in the serde_json crate. The arbitrary_precision feature causes numbers to be stored as strings, so perhaps to_dataset_for_signing is incorrectly canonicalizing numbers as strings.

The specific error returned by Credential::verify / Presentation::verify is "Verification equation was not satisfied" if ed25519-dalek is used, and "ring::error::Unspecified" if ring is used.