What does this PR do?

Fixes #28687

When a URL contains repeated query parameters (e.g., /john?user=john&user=doe), Next.js parses them as string[]. Passing context.query cast to Record<string, string> into URLSearchParams serializes arrays as comma-separated strings (user=john%2Cdoe), breaking downstream logic.

Fix

Replace the cast with explicit iteration using URLSearchParams.append() per value:

// Before — array values collapsed to comma-separated string
new URLSearchParams(context.query as Record<string, string>)

// After — each value appended individually
const queryParams = new URLSearchParams();
for (const [key, value] of Object.entries(context.query)) {
  if (Array.isArray(value)) {
    value.forEach((v) => queryParams.append(key, v));
  } else if (value !== undefined) {
    queryParams.append(key, value);
  }
}

Changes

• apps/web/server/lib/[user]/getServerSideProps.ts — fix query string serialization in dynamic group redirect