Fix redirect issues

Dashboard button now correctly redirects to login page if user is not
logged in while login page redirects to dashboard the other way around.

src/routes/login.rs

@@ -6,12 +6,15 @@ use crate::{
     templates::ErrorTemplate,
 };
 use askama::Template;
-use axum::http::{HeaderMap, StatusCode};
 use axum::{
     Form, Json,
     extract::State,
     response::{Html, IntoResponse, Response},
 };
+use axum::{
+    http::{HeaderMap, StatusCode},
+    response::Redirect,
+};
 use secrecy::SecretString;
 
 #[derive(thiserror::Error)]
@@ -65,8 +68,17 @@ pub struct LoginFormData {
     password: SecretString,
 }
 
-pub async fn get_login() -> Html<String> {
-    Html(LoginTemplate.render().unwrap())
+pub async fn get_login(session: TypedSession) -> Result<Response, LoginError> {
+    if session
+        .get_user_id()
+        .await
+        .map_err(|e| LoginError::UnexpectedError(e.into()))?
+        .is_some()
+    {
+        Ok(Redirect::to("/admin/dashboard").into_response())
+    } else {
+        Ok(Html(LoginTemplate.render().unwrap()).into_response())
+    }
 }
 
 pub async fn post_login(