Use serde(rename)

[sosthene-nitrokey]

No description provided.

[sosthene-nitrokey]

trussed-auth also creates a lot of intermediate files. Maybe we should consider migrating to removing the dat intermediary folders for the backend. That would require overriding the filestore to allow it to optionally remove the dat.

For example for a single PIN in the secrets app:

 /
├──  backend-auth
│   └──  dat
│       └── [  16]  salt
├──  secrets
│   └──  backend-auth
│       └──  dat
│           ├── [  16]  application_salt
│           └── [ 118]  pin.00
└──  trussed
    └── dat
        └── [  32]  rng-state.bin

This is also made worse when both the software impl of trussed-auth and the SE050 impl are used.

[robin-nitrokey]

Missing changelog entry, otherwise LGTM!