retry-after header missing from response

[aleclarson]

If there's no retry-after or retry-after-ms response header, the library should create one from the greater value of the anthropic-ratelimit-requests-reset and anthropic-ratelimit-tokens-reset headers (if both anthropic-ratelimit-requests-remaining and anthropic-ratelimit-tokens-remaining are zero). If only one of those headers is zero, use the reset time for that one.

{
    'anthropic-ratelimit-requests-limit': '5',
    'anthropic-ratelimit-requests-remaining': '0',
    'anthropic-ratelimit-requests-reset': '2024-03-26T20:00:00Z',
    'anthropic-ratelimit-tokens-limit': '25000',
    'anthropic-ratelimit-tokens-remaining': '16000',
    'anthropic-ratelimit-tokens-reset': '2024-03-26T20:00:00Z',
    'cf-cache-status': 'DYNAMIC',
    'cf-ray': '86a9b96cdac90359-MIA',
    connection: 'keep-alive',
    'content-length': '305',
    'content-type': 'application/json',
    date: 'Tue, 26 Mar 2024 19:59:59 GMT',
    'request-id': 'req_01T5fCVnYdf9X5ZW6KayReBK',
    server: 'cloudflare',
    via: '1.1 google',
    'x-cloud-trace-context': 'ae6af598607da922ea75fbb21d9c3bd6',
    'x-should-retry': 'true'
  }

[rattrayalex]

Hey, thanks for raising this. I've pinged the relevant folks on the API team to see if we can't just get retry-after-ms sent on every 429.