chore: upgrade Rust toolchain to 1.89 and modernize code with let-chains

server/Cargo.toml

@@ -9,6 +9,7 @@ authors.workspace = true
 homepage.workspace = true
 license.workspace = true
 repository.workspace = true
+rust-version.workspace = true
 
 [dependencies]
 actix = "0.13"

server/tests/common/graphql.rs

@@ -1,3 +1,4 @@
+#![allow(dead_code)]
 use crate::common::env;
 use anyhow::{Context, Result, anyhow};
 use graphql_client::GraphQLQuery;