Rework SecretKey API to facilitate async (#371)

* Rework `SecretKey` API to facilitate async

* Remove left-over constraints

Cargo.toml

@@ -17,7 +17,7 @@ curve25519 = ["dep:curve25519-dalek"]
 default = ["ristretto255-voprf", "serde"]
 ristretto255 = ["dep:curve25519-dalek", "voprf/ristretto255"]
 ristretto255-voprf = ["ristretto255", "voprf/ristretto255-ciphersuite"]
-serde = ["dep:serde", "generic-array/serde", "voprf/serde"]
+serde = ["dep:serde", "generic-array/serde", "voprf/serde", "zeroize/serde"]
 std = ["dep:getrandom"]
 
 [dependencies]
@@ -27,7 +27,7 @@ argon2 = { version = "0.5", default-features = false, features = [
 curve25519-dalek = { version = "4", default-features = false, features = [
   "zeroize",
 ], optional = true }
-derive-where = { version = "1", features = ["zeroize-on-drop"] }
+derive-where = { version = "1.3", features = ["zeroize-on-drop"] }
 digest = "0.10"
 displaydoc = { version = "0.2", default-features = false }
 elliptic-curve = { version = "0.13", features = ["hash2curve", "sec1"] }
@@ -46,25 +46,32 @@ zeroize = { version = "1.8", features = ["zeroize_derive"] }
 getrandom = { version = "0.2", features = ["js"], optional = true }
 
 [dev-dependencies]
+anyhow = "1"
 bincode = "1"
 chacha20poly1305 = "0.10"
 criterion = "0.5"
+cryptoki = "0.9"
+elliptic-curve = { version = "0.13", features = ["alloc", "pkcs8"] }
 hex = "0.4"
 p256 = { version = "0.13", default-features = false, features = [
   "hash2curve",
+  "pkcs8",
   "voprf",
 ] }
 p384 = { version = "0.13", default-features = false, features = [
   "hash2curve",
+  "pkcs8",
   "voprf",
 ] }
 p521 = { version = "0.13.3", default-features = false, features = [
   "hash2curve",
+  "pkcs8",
   "voprf",
 ] }
 proptest = "1"
 rand = "0.8"
 regex = "1"
+thiserror = "2"
 # MSRV
 rustyline = "15"
 scrypt = "0.11"
@@ -82,3 +89,6 @@ targets = []
 [[example]]
 name = "simple_login"
 required-features = ["argon2"]
+
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(test_hsm)'] }