feat: implement session-based authentication and core API handlers for user management

backend/src/handlers/diets.rs

@@ -0,0 +1,36 @@
+//! Diet API handlers.
+
+use axum::{extract::State, http::StatusCode, Json};
+use sea_orm::{DatabaseConnection, EntityTrait};
+use serde::Serialize;
+
+use crate::models::user::diet;
+
+/// Response for a diet type.
+#[derive(Serialize)]
+pub struct DietResponse {
+    pub id: i32,
+    pub name: String,
+    pub description: Option<String>,
+}
+
+/// GET /api/diets - List all diet types for UI dropdown.
+pub async fn list_diets(
+    State(db): State<DatabaseConnection>,
+) -> Result<Json<Vec<DietResponse>>, StatusCode> {
+    let diets = diet::Entity::find()
+        .all(&db)
+        .await
+        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
+
+    let items: Vec<DietResponse> = diets
+        .into_iter()
+        .map(|d| DietResponse {
+            id: d.id,
+            name: d.name,
+            description: d.description,
+        })
+        .collect();
+
+    Ok(Json(items))
+}