Add missing response fields for pagination

[albertpurnama]

Describe the change
Missing pagination parameters for new assistants list API

Describe your solution
Add missing parameters

Tests
Verified against endpoint

Additional context

curl https://api.openai.com/v1/threads/thread_abc123/messages \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $OPENAI_API_KEY" \
  -H "OpenAI-Beta: assistants=v1"
{
  "object": "list",
  "data": [],
  "first_id": "msg_abc123",
  "last_id": "msg_abc456",
  "has_more": false
}

Issue: resolves #583
Similar PR: #571

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1846572) 98.38% compared to head (c2d2b4e) 98.38%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #584   +/-   ##
=======================================
  Coverage   98.38%   98.38%           
=======================================
  Files          24       24           
  Lines        1300     1300           
=======================================
  Hits         1279     1279           
  Misses         15       15           
  Partials        6        6           

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[sashabaranov]

Thank you!