More tests, not found page and dashboard fixes

When post was deleted, website shows a 404 page insead of an 500 page.
Also made the dashboard empty page message more explicit.

src/routes/posts.rs

@@ -1,8 +1,8 @@
 use crate::{
     domain::PostEntry,
-    routes::AppError,
+    routes::{AppError, not_found},
     startup::AppState,
-    templates::{PostListTemplate, PostTemplate, PostsTemplate},
+    templates::{HtmlTemplate, PostListTemplate, PostTemplate, PostsTemplate},
 };
 use anyhow::Context;
 use askama::Template;
@@ -75,27 +75,41 @@ pub async fn see_post(
     Query(PostParams { origin }): Query<PostParams>,
 ) -> Result<Response, AppError> {
     if let Some(origin) = origin {
-        sqlx::query!(
-            "UPDATE notifications_delivered SET opened = TRUE WHERE email_id = $1",
-            origin,
-        )
-        .execute(&connection_pool)
-        .await
-        .context("Failed to mark email as opened.")
-        .map_err(AppError::unexpected_page)?;
+        mark_email_as_opened(&connection_pool, origin).await?;
         return Ok(Redirect::to(&format!("/posts/{}", post_id)).into_response());
     }
-    let post = get_post_data(&connection_pool, post_id)
+
+    if let Some(post) = get_post_data(&connection_pool, post_id)
         .await
         .context(format!("Failed to fetch post #{}", post_id))
         .map_err(AppError::unexpected_page)?
-        .to_html()
-        .context("Could not render markdown with extension.")?;
-    let template = PostTemplate { post };
-    Ok(Html(template.render().unwrap()).into_response())
+    {
+        let post = post
+            .to_html()
+            .context("Could not render markdown with extension.")?;
+        let template = HtmlTemplate(PostTemplate { post });
+        Ok(template.into_response())
+    } else {
+        Ok(not_found().await)
+    }
 }
 
-async fn get_post_data(connection_pool: &PgPool, post_id: Uuid) -> Result<PostEntry, sqlx::Error> {
+async fn mark_email_as_opened(connection_pool: &PgPool, email_id: Uuid) -> Result<(), AppError> {
+    sqlx::query!(
+        "UPDATE notifications_delivered SET opened = TRUE WHERE email_id = $1",
+        email_id,
+    )
+    .execute(connection_pool)
+    .await
+    .context("Failed to mark email as opened.")
+    .map_err(AppError::unexpected_page)?;
+    Ok(())
+}
+
+async fn get_post_data(
+    connection_pool: &PgPool,
+    post_id: Uuid,
+) -> Result<Option<PostEntry>, sqlx::Error> {
     sqlx::query_as!(
         PostEntry,
         r#"
@@ -106,7 +120,7 @@ async fn get_post_data(connection_pool: &PgPool, post_id: Uuid) -> Result<PostEn
         "#,
         post_id
     )
-    .fetch_one(connection_pool)
+    .fetch_optional(connection_pool)
     .await
 }