feat: add new method to create secret from keys

Author: emmanuelm41

.gitignore

@@ -1,2 +1,3 @@
 /Cargo.lock
 /target
+.idea

src/participant.rs

@@ -8,10 +8,11 @@ use core::cell::OnceCell;
 use core::cmp;
 use core::hash::Hash;
 use core::hash::Hasher;
-use ed25519_dalek::Signer;
+use ed25519_dalek::{Signer, SECRET_KEY_LENGTH};
 use ed25519_dalek::SigningKey;
 use ed25519_dalek::Verifier;
 use ed25519_dalek::VerifyingKey;
+use ed25519_dalek::SecretKey;
 use rand_core::CryptoRng;
 use rand_core::RngCore;
 use x25519_dalek::PublicKey;
@@ -80,6 +81,15 @@ impl Secret {
         }
     }
 
+    #[must_use]
+    pub fn from_secret_keys(secret_key_1: &SecretKey, secret_key_2: &SecretKey) -> Self {
+        Self {
+            signing_key: SigningKey::from_bytes(secret_key_1),
+            decryption_key: StaticSecret::from(*secret_key_2),
+            identity: OnceCell::new(),
+        }
+    }
+
     #[inline]
     #[must_use]
     pub fn signing_key(&self) -> &SigningKey {