add webpack5 for nextjs v9.5 (#3572)

packages/datadog-plugin-next/test/index.spec.js

@@ -79,6 +79,12 @@ describe('Plugin', function () {
 
         delete pkg.workspaces
 
+        // builds fail for next.js 9.5 using node 14 due to webpack issues
+        // note that webpack version cannot be set in v9.5 in next.config.js so we do it here instead
+        // the link below highlights the initial support for webpack 5 (used to fix this issue) in next.js 9.5
+        // https://nextjs.org/blog/next-9-5#webpack-5-support-beta
+        if (realVersion.startsWith('9')) pkg.resolutions = { webpack: '^5.0.0' }
+
         writeFileSync(`${__dirname}/package.json`, JSON.stringify(pkg, null, 2))
 
         // installing here for standalone purposes, copying `nodules` above was not generating the server file properly