Develop first version (#1)

Create first version of the library

The code is mainly taken from

* https://gitea.communiquons.org/pierre/oidc-test-client
* https://gitea.communiquons.org/pierre/BasicOIDC

with little improvements.

Reviewed-on: #1

src/time_utils.rs

@@ -0,0 +1,19 @@
+use std::time::{SystemTime, UNIX_EPOCH};
+
+/// Get current time since epoch, in seconds
+pub fn time() -> u64 {
+    SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .unwrap()
+        .as_secs()
+}
+
+#[cfg(test)]
+mod test {
+    use crate::time_utils::time;
+
+    #[test]
+    fn time_is_recent_enough() {
+        assert!(time() > 1682750570);
+    }
+}