feat: add visibility feature to thoughts, including new enum, database migration, and update related endpoints and tests

thoughts-backend/api/src/extractor/optional_auth.rs

@@ -0,0 +1,21 @@
+use super::AuthUser;
+use crate::error::ApiError;
+use app::state::AppState;
+use axum::{extract::FromRequestParts, http::request::Parts};
+
+pub struct OptionalAuthUser(pub Option<AuthUser>);
+
+impl FromRequestParts<AppState> for OptionalAuthUser {
+    type Rejection = ApiError;
+
+    async fn from_request_parts(
+        parts: &mut Parts,
+        state: &AppState,
+    ) -> Result<Self, Self::Rejection> {
+        match AuthUser::from_request_parts(parts, state).await {
+            Ok(user) => Ok(OptionalAuthUser(Some(user))),
+            // If the user is not authenticated for any reason, we just treat them as a guest.
+            Err(_) => Ok(OptionalAuthUser(None)),
+        }
+    }
+}