bugfix: ignore enumerable functions when copying headers in Pages-router

[tusharpandey13]

Updates createRequestCookies to avoid treating helper functions on req.headers as header values, preventing runtime crashes on Node 20+.

• All new/changed/fixed functionality is covered by tests
• I have added documentation for all new/changed functionality (N/A)

🔍 RCA

for…in over req.headers also enumerated prototype helper methods (append, delete, …) starting Node 20. Passing these functions to the WHATWG Headers API raised TypeError: <fn> is an invalid header value when auth0.updateSession() ran in a Pages-router route.

📋 Changes

Changed nextjs-auth0/src/server/client.ts: iterate over Object.entries(req.headers) and copy only string|string[] values; updated docstring
Added nextjs-auth0/tests/createRequestCookies-header-copy.test.ts: regression tests that reproduce the crash and assert correct cookie parsing

📎 References

• Fixes: Headers.append: xxx is an invalid header value #2219

🎯 Testing

Automated:

• New Vitest spec tests/createRequestCookies-header-copy.test.ts fails on pre-patch code, passes now.
• pnpm run test:coverage shows all 248 tests passing with > 84 % coverage.

Manual:

1. Build SDK: pnpm run build
2. Integrate via yalc into sample app on Node 22
3. Hit endpoint that calls auth0.updateSession
4. Confirm no Headers.append error and session updates as expected.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 77.77778% with 2 lines in your changes missing coverage. Please review.

Project coverage is 85.01%. Comparing base (15e7511) to head (b455689).

Files with missing lines	Patch %	Lines
src/server/client.ts	77.77%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2225      +/-   ##
==========================================
+ Coverage   84.54%   85.01%   +0.46%     
==========================================
  Files          22       22              
  Lines        2233     2236       +3     
  Branches      406      413       +7     
==========================================
+ Hits         1888     1901      +13     
+ Misses        339      329      -10     
  Partials        6        6              

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