Added first implementation of RP Initiated Logout

Created a new extractor for RP-Initiated-Logout and modified example to
use it.

src/extractor.rs

@@ -1,9 +1,13 @@
-use std::ops::Deref;
+use std::{borrow::Cow, ops::Deref};
 
 use crate::{error::ExtractorError, AdditionalClaims};
 use async_trait::async_trait;
-use axum_core::extract::FromRequestParts;
-use http::request::Parts;
+use axum::response::Redirect;
+use axum_core::{
+    extract::FromRequestParts,
+    response::{IntoResponse, Response},
+};
+use http::{request::Parts, uri::PathAndQuery, Uri};
 use openidconnect::{core::CoreGenderClaim, IdTokenClaims};
 
 /// Extractor for the OpenID Connect Claims.
@@ -81,3 +85,80 @@ impl AsRef<str> for OidcAccessToken {
         self.0.as_str()
     }
 }
+
+#[derive(Clone)]
+pub struct OidcRpInitiatedLogout {
+    pub(crate) end_session_endpoint: Uri,
+    pub(crate) id_token_hint: String,
+    pub(crate) client_id: String,
+    pub(crate) post_logout_redirect_uri: Option<Uri>,
+    pub(crate) state: Option<String>,
+}
+
+impl OidcRpInitiatedLogout {
+    pub fn with_post_logout_redirect(mut self, uri: Uri) -> Self {
+        self.post_logout_redirect_uri = Some(uri);
+        self
+    }
+    pub fn with_state(mut self, state: String) -> Self {
+        self.state = Some(state);
+        self
+    }
+    pub fn uri(self) -> Uri {
+        let mut parts = self.end_session_endpoint.into_parts();
+
+        let query = {
+            let mut query = Vec::with_capacity(4);
+            query.push(("id_token_hint", Cow::Borrowed(&self.id_token_hint)));
+            query.push(("client_id", Cow::Borrowed(&self.client_id)));
+
+            if let Some(post_logout_redirect_uri) = &self.post_logout_redirect_uri {
+                query.push((
+                    "post_logout_redirect_uri",
+                    Cow::Owned(post_logout_redirect_uri.to_string()),
+                ));
+            }
+            if let Some(state) = &self.state {
+                query.push(("state", Cow::Borrowed(state)));
+            }
+
+            query
+                .into_iter()
+                .map(|(k, v)| format!("{}={}", k, urlencoding::encode(v.as_str())))
+                .collect::<Vec<_>>()
+                .join("&")
+        };
+
+        let path_and_query = match parts.path_and_query {
+            Some(path_and_query) => {
+                PathAndQuery::from_maybe_shared(format!("{}?{}", path_and_query.path(), query))
+            }
+            None => PathAndQuery::from_maybe_shared(format!("?{}", query)),
+        };
+        parts.path_and_query = Some(path_and_query.unwrap());
+
+        Uri::from_parts(parts).unwrap()
+    }
+}
+#[async_trait]
+impl<S> FromRequestParts<S> for OidcRpInitiatedLogout
+where
+    S: Send + Sync,
+{
+    type Rejection = ExtractorError;
+
+    async fn from_request_parts(parts: &mut Parts, _: &S) -> Result<Self, Self::Rejection> {
+        parts
+            .extensions
+            .get::<Self>()
+            .cloned()
+            .ok_or(ExtractorError::Unauthorized)
+    }
+}
+
+#[async_trait]
+impl IntoResponse for OidcRpInitiatedLogout {
+    fn into_response(self) -> Response {
+        Redirect::temporary(&self.uri().to_string()).into_response()
+    }
+}