Use testcontainers host for Postgres tests

crates/crank-test-support/src/lib.rs

@@ -90,13 +90,16 @@ fn start_postgres() -> TestPostgres {
         .start()
         .expect("test PostgreSQL container must start");
     register_container_cleanup(container.id().to_owned());
+    let host = container
+        .get_host()
+        .expect("test PostgreSQL host must be resolved");
     let port = container
         .get_host_port_ipv4(5432)
         .expect("test PostgreSQL port must be mapped");
 
     TestPostgres {
         _container: container,
-        database_url: format!("postgres://crank:crank@127.0.0.1:{port}/crank"),
+        database_url: format!("postgres://crank:crank@{host}:{port}/crank"),
     }
 }