Content Negotiation

  Accept                                                 → 服务端提供 ['application/json', 'text/html', 'text/csv'] 时选择
  */*                                                    → 200 application/json   curl 默认
  application/json                                       → 200 application/json   
  text/html                                              → 200 text/html; charset=utf-8   
  text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 → 200 text/html; charset=utf-8   Chrome 的导航请求
  application/json, text/html                            → 200 application/json   同 q 值
  text/html, application/json                            → 200 application/json   同 q 值,顺序相反
  application/json;q=0.5, text/html;q=0.9                → 200 text/html; charset=utf-8   
  text/*                                                 → 200 text/html; charset=utf-8   
  image/png                                              → 406 application/json   服务端没有的
  application/json;q=0                                   → 406 application/json   q=0 表示不接受
  text/html;q=0, */*;q=0.1                               → 200 application/json   
  (无)                                                    → 406 application/json   没有 Accept 头
  garbage                                                → 406 application/json   

   {'accept_html': True, 'accept_json': True, 'best': 'text/html', 'json_in': True, 'quality_json': 0.8, 'values': [['text/html', 1], ['application/xhtml+xml', 1], ['application/xml', 0.9], ['*/*', 0.8]]}

  Accept: image/png → 406 {'error': 'not acceptable', 'offered': ['application/json', 'text/html', 'text/csv']} | Vary = Accept
  Accept: application/json → Vary = Accept

  Accept-Language: zh-CN,zh;q=0.9,en;q=0.8    → best_match(zh-CN, zh-TW, en, en-GB, ja; default=en) = zh-CN
  Accept-Language: zh                         → best_match(zh-CN, zh-TW, en, en-GB, ja; default=en) = zh-CN
  Accept-Language: zh-TW                      → best_match(zh-CN, zh-TW, en, en-GB, ja; default=en) = zh-TW
  Accept-Language: en-US,en;q=0.9             → best_match(zh-CN, zh-TW, en, en-GB, ja; default=en) = en
  Accept-Language: fr                         → best_match(zh-CN, zh-TW, en, en-GB, ja; default=en) = en
  Accept-Language: ja;q=0.5, en;q=0.9         → best_match(zh-CN, zh-TW, en, en-GB, ja; default=en) = en
  Accept-Language: *                          → best_match(zh-CN, zh-TW, en, en-GB, ja; default=en) = zh-CN
  Accept-Language: (无)                        → best_match(zh-CN, zh-TW, en, en-GB, ja; default=en) = en

  gzip, deflate, br                  → gzip q=1 br q=1 identity q=0
  gzip;q=0, identity                 → gzip q=0.0 br q=0 identity q=1
  br;q=1.0, gzip;q=0.8, *;q=0.1      → gzip q=0.8 br q=1.0 identity q=0.1
  (无)                                → gzip q=0 br q=0 identity q=0

  GET /ext.json  → 200 application/json
  GET /ext.html  → 200 text/html; charset=utf-8
  GET /ext.xml   → 404 text/html; charset=utf-8

  curl 默认: {"accept":"*/*","ae":null,"ua":"curl/8.7.1"}
  requests 默认: {"accept":"*/*","ae":"gzip, deflate, zstd","ua":"python-requests/2.34.2"}