added an example for ed25519 (#282)

Co-authored-by: Ovidiu Ionescu <ovidiu@ionescu.net>

examples/ed25519.rs

@@ -0,0 +1,62 @@
+use jsonwebtoken::{
+    decode, encode, get_current_timestamp, Algorithm, DecodingKey, EncodingKey, Validation,
+};
+use ring::signature::{Ed25519KeyPair, KeyPair};
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct Claims {
+    sub: String,
+    exp: u64,
+}
+
+fn main() {
+    let doc = Ed25519KeyPair::generate_pkcs8(&ring::rand::SystemRandom::new()).unwrap();
+    let encoding_key = EncodingKey::from_ed_der(doc.as_ref());
+
+    let pair = Ed25519KeyPair::from_pkcs8(doc.as_ref()).unwrap();
+    let decoding_key = DecodingKey::from_ed_der(pair.public_key().as_ref());
+
+    let claims = Claims { sub: "test".to_string(), exp: get_current_timestamp() };
+
+    let token =
+        encode(&jsonwebtoken::Header::new(Algorithm::EdDSA), &claims, &encoding_key).unwrap();
+
+    let validation = Validation::new(Algorithm::EdDSA);
+    let _token_data = decode::<Claims>(&token, &decoding_key, &validation).unwrap();
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    struct Jot {
+        encoding_key: EncodingKey,
+        decoding_key: DecodingKey,
+    }
+
+    impl Jot {
+        fn new() -> Jot {
+            let doc = Ed25519KeyPair::generate_pkcs8(&ring::rand::SystemRandom::new()).unwrap();
+            let encoding_key = EncodingKey::from_ed_der(doc.as_ref());
+
+            let pair = Ed25519KeyPair::from_pkcs8(doc.as_ref()).unwrap();
+            let decoding_key = DecodingKey::from_ed_der(pair.public_key().as_ref());
+            Jot { encoding_key, decoding_key }
+        }
+    }
+
+    #[test]
+    fn test() {
+        let jot = Jot::new();
+        let claims = Claims { sub: "test".to_string(), exp: get_current_timestamp() };
+
+        let token =
+            encode(&jsonwebtoken::Header::new(Algorithm::EdDSA), &claims, &jot.encoding_key)
+                .unwrap();
+
+        let validation = Validation::new(Algorithm::EdDSA);
+        let token_data = decode::<Claims>(&token, &jot.decoding_key, &validation).unwrap();
+        assert_eq!(token_data.claims.sub, "test");
+    }
+}