Implemented userinfo endpoint and finalized OAuth2.0 flow

src/util.rs

@@ -6,6 +6,18 @@ use log::{LevelFilter, error, info};
 use simplelog::{ColorChoice, CombinedLogger, TermLogger, TerminalMode, WriteLogger};
 use std::fs::File;
 use std::sync::Arc;
+use serde::de::DeserializeOwned;
+use base64::{engine::general_purpose::URL_SAFE_NO_PAD, Engine as _};
+
+pub fn decode_payload_unchecked<T: DeserializeOwned>(token: &str) -> Result<T, Box<dyn std::error::Error>> {
+    let mut parts = token.split('.');
+    let _header = parts.next().ok_or("missing header")?;
+    let payload_b64 = parts.next().ok_or("missing payload")?;
+    // signature is parts.next() but we ignore it here
+    let payload = URL_SAFE_NO_PAD.decode(payload_b64.as_bytes())?;
+    let claims = serde_json::from_slice::<T>(&payload)?;
+    Ok(claims)
+}
 
 pub fn initialize_logging(config: &Config) {
     CombinedLogger::init(vec![