Implemented data model, database schema and database connection pool.

src/backend/mod.rs

@@ -0,0 +1,26 @@
+use cfg_if::cfg_if;
+
+pub mod data;
+
+cfg_if!{
+    if #[cfg(feature = "ssr")] {
+        use sqlx::PgPool;
+
+        #[derive(Clone)]
+        pub struct AppData {
+            db_pool: PgPool
+        }
+
+        impl AppData {
+            pub fn new(db_pool: PgPool) -> Self {
+                Self {
+                    db_pool
+                }
+            }
+
+            pub fn db_pool(&self) -> &PgPool {
+                &self.db_pool
+            }
+        }
+    }
+}