Use immutable updates for CSS loader configuration

[justin808]

Issue

Currently in config/webpack/commonWebpackConfig.js:49-61, we directly mutate nested loader options:

if (cssLoader?.options?.modules) {
  cssLoader.options.modules.namedExport = false;
  cssLoader.options.modules.exportLocalsConvention = 'camelCase';
}

This risks affecting shared objects from Shakapacker's defaults.

Solution

Use object spread for immutability (already done correctly in serverWebpackConfig.js):

if (cssLoader?.options?.modules) {
  cssLoader.options.modules = {
    ...cssLoader.options.modules,
    namedExport: false,
    exportLocalsConvention: 'camelCase',
  };
}

Related

Similar pattern needed in Sass loader configuration (lines 80-96).