feat: backend service

integration/testenv/io.go

@@ -0,0 +1,10 @@
+package testenv
+
+import "os"
+
+// writeFileFn is a tiny indirection so other files in this package can
+// write fixtures without re-declaring os.WriteFile and to keep test
+// hooks centralised.
+func writeFileFn(path string, content []byte) error {
+	return os.WriteFile(path, content, 0o600)
+}