fido2: hide "FIDO2" in gocryptfs.conf if not used
Result of:
$ gocryptfs -init foo
$ cat foo/gocryptfs.conf
Before:
{
"Creator": "gocryptfs v2.0.1",
"EncryptedKey": "FodEdNHD/cCwv1n5BuyAkbIOnJ/O5gfdCh3YssUCJ2DUr0A8DrQ5NH2SLhREeWRL3V8EMiPO2Ncr5IVwE4SSxQ==",
"ScryptObject": {
"Salt": "brGaw9Jg1kbPuSXFiwoxqK2oXFTgbniSgpiB+cu+67Y=",
"N": 65536,
"R": 8,
"P": 1,
"KeyLen": 32
},
"Version": 2,
"FeatureFlags": [
"GCMIV128",
"HKDF",
"DirIV",
"EMENames",
"LongNames",
"Raw64"
],
"FIDO2": {
"CredentialID": null,
"HMACSalt": null
}
}
After:
{
"Creator": "gocryptfs v2.0.1-5-gf9718eb-dirty.DerDonut-badnamecontent",
"EncryptedKey": "oFMj1lS1ZsM/vEfanNMeCTPw3PZr5VWeL7ap8Jd8YQm6evy2BAhtQ/pd6RzDx84wlCz9TpxqHRihuwSEMnOWWg==",
"ScryptObject": {
"Salt": "JZ/5mhy4a8EAQ/wDF1POIEe4/Ss38cfJgXgj26DuA4M=",
"N": 65536,
"R": 8,
"P": 1,
"KeyLen": 32
},
"Version": 2,
"FeatureFlags": [
"GCMIV128",
"HKDF",
"DirIV",
"EMENames",
"LongNames",
"Raw64"
]
}