Move database into the main app

I was having issues including the lib as a crate, its fine just being a
module for now.

src/database/models.rs

@@ -0,0 +1,17 @@
+use crate::database::schema::users;
+use serde::Serialize;
+
+#[derive(Insertable)]
+#[table_name = "users"]
+pub struct InsertUser<'a> {
+    pub username: &'a str,
+    pub password: &'a str,
+}
+
+#[derive(Serialize, Queryable, Clone, Debug)]
+pub struct User {
+    pub id: i32,
+    pub username: String,
+    #[serde(skip_serializing)]
+    pub password: String,
+}