Add code challenge support

src/actors/openid_sessions_actor.rs

@@ -3,6 +3,7 @@ use actix::Message;
 
 use crate::constants::*;
 use crate::data::client::ClientID;
+use crate::data::code_challenge::CodeChallenge;
 use crate::data::user::UserID;
 use crate::utils::time::time;
 
@@ -27,7 +28,7 @@ pub struct Session {
     pub refresh_token_expire_at: u64,
 
     pub nonce: Option<String>,
-    pub code_challenge: Option<(String, String)>,
+    pub code_challenge: Option<CodeChallenge>,
 }
 
 impl Session {