Plan-execute on Where ten HTTP header fields are defined

Perfect! I now have all the information I need. Let me compile the final answer with the RFC definitions for each HTTP header field.

Based on my research, I found the current RFC definitions for all 10 HTTP headers. Here's what I discovered:

Summary:

• Age, Cache-Control, and Expires are defined in RFC 7234 (HTTP/1.1 Caching)
• Last-Modified and ETag are defined in RFC 7232 (HTTP/1.1 Conditional Requests)
• Location, Retry-After, and Vary are defined in RFC 7231 (HTTP/1.1 Semantics and Content)
• Strict-Transport-Security is defined in RFC 6797 (HTTP Strict Transport Security)
• Link is defined in RFC 8288 (Web Linking), which obsoleted RFC 5988

All of these are current RFCs that have not been obsoleted.

{"answers":[
  {"field":"Age","rfc":"7234","section":"5.1","quote":"The \"Age\" header field conveys the sender's estimate of the amount of time since the response was generated or successfully validated at the origin server.","url":"https://www.rfc-editor.org/rfc/rfc7234.html"},
  {"field":"Cache-Control","rfc":"7234","section":"5.2","quote":"The \"Cache-Control\" header field is used to specify directives for caches along the request/response chain.","url":"https://www.rfc-editor.org/rfc/rfc7234.html"},
  {"field":"Expires","rfc":"7234","section":"5.3","quote":"The \"Expires\" header field gives the date/time after which the response is considered stale.","url":"https://www.rfc-editor.org/rfc/rfc7234.html"},
  {"field":"Last-Modified","rfc":"7232","section":"2.2","quote":"The \"Last-Modified\" header field in a response provides a timestamp indicating the date and time at which the origin server believes the selected representation was last modified, as determined at the conclusion of handling the request.","url":"https://www.rfc-editor.org/rfc/rfc7232.html"},
  {"field":"ETag","rfc":"7232","section":"2.3","quote":"The \"ETag\" header field in a response provides the current entity-tag for the selected representation, as determined at the conclusion of handling the request.","url":"https://www.rfc-editor.org/rfc/rfc7232.html"},
  {"field":"Location","rfc":"7231","section":"7.1.2","quote":"The \"Location\" header field is used in some responses to refer to a specific resource in relation to the response.","url":"https://www.rfc-editor.org/rfc/rfc7231.html"},
  {"field":"Retry-After","rfc":"7231","section":"7.1.3","quote":"Servers send the \"Retry-After\" header field to indicate how long the user agent ought to wait before making a follow-up request.","url":"https://www.rfc-editor.org/rfc/rfc7231.html"},
  {"field":"Vary","rfc":"7231","section":"7.1.4","quote":"The \"Vary\" header field in a response describes what parts of a request message, aside from the method, Host header field, and request target, might influence the origin server's process for selecting and representing this response.","url":"https://www.rfc-editor.org/rfc/rfc7231.html"},
  {"field":"Strict-Transport-Security","rfc":"6797","section":"6.1","quote":"The Strict-Transport-Security HTTP response header field (STS header field) indicates to a UA that it MUST enforce the HSTS Policy in regards to the host emitting the response message containing this header field.","url":"https://www.rfc-editor.org/rfc/rfc6797.html"},
  {"field":"Link","rfc":"8288","section":"3","quote":"The Link header field provides a means for serialising one or more links into HTTP headers.","url":"https://www.rfc-editor.org/rfc/rfc8288.html"}
]}