Add allow warnings for nonstandard macro braces

The warnings come from the macros of libraries that we use, so we can't
change them.

app/src/lib.rs

@@ -1,4 +1,5 @@
 #![recursion_limit = "256"]
+#![allow(clippy::nonstandard_macro_braces)]
 mod api;
 mod app;
 mod cookies;

model/src/lib.rs

@@ -1,3 +1,4 @@
+#![allow(clippy::nonstandard_macro_braces)]
 use chrono::prelude::*;
 use serde::{Deserialize, Serialize};
 use std::collections::HashSet;

src/main.rs

@@ -1,4 +1,6 @@
 #![forbid(unsafe_code)]
+#![allow(clippy::nonstandard_macro_braces)]
+
 use crate::{
     domain::{
         handler::BackendHandler, sql_backend_handler::SqlBackendHandler, sql_tables::PoolOptions,