api to create encrypted header

Summary:
## Context

- Design doc:
https://docs.google.com/document/d/1oAxFfQDJ2Ti3NH981jW-okfcrx4cPRo6N8FWKUp5WxM/edit#heading=h.g9v8c7dr6d6o
- Context: https://fb.workplace.com/groups/proxygendevelopers/posts/1033854548378587/?comment_id=1040393961057979

## This diff
- Create a `createProxyStatusEncrypted` function.
  - We'll call this function at multiple places in DFSRouter for 429/503 responses.
  - Next half, Traffic team plans to have a KR to make our proxy-status header library RFC compliant. We plan to modify this function like this:

```
ProxyStatusEncrypted createProxyStatusHeader(StatusType statusType, std::string& proxy, std::string& details) {
  if (use legacy format) {
    // Example result:
    // `Proxy-Status: http_request_error; e_proxy="dfsrouter"; details="DFSRouter RPS Throttling"`

  } else {
    // Example result:
    // `Proxy-Status: "dfsrouter"; error=http_request_error; details="DFSRouter RPS Throttling"`

  }
}
```
- Add the [standard field "details"](https://www.rfc-editor.org/rfc/rfc9209.html#section-2.1.5) to ProxyStatus class.

Reviewed By: mjsaltus

Differential Revision: D62532980

fbshipit-source-id: 078533998927eac01ca9ecc0264410bfd4b573d1

third-party/proxygen/src/proxygen/lib/http/ProxyStatus.cpp

@@ -18,6 +18,7 @@ constexpr folly::StringPiece kIsProxyErrorParam{"e_isproxyerr"};
 constexpr folly::StringPiece kIsClientErrorTrue{"e_isclienterr"};
 constexpr folly::StringPiece kIsServerErrorTrue{"e_isservererr"};
 constexpr folly::StringPiece kClientAddrParam{"e_clientaddr"};
+constexpr folly::StringPiece kDetails{"details"};
 
 } // namespace
 
@@ -83,6 +84,10 @@ ProxyStatus& ProxyStatus::setClientAddress(const std::string& clientAddr) {
  return setProxyStatusParameter(kClientAddrParam, clientAddr);
 }
 
+ProxyStatus& ProxyStatus::setDetails(const std::string& details) {
+ return setProxyStatusParameter(kDetails, details);
+}
+
 bool ProxyStatus::hasUpstreamIP() const {
  return pIdent_.parameterMap.find(std::string(kUpstreamIPParam)) !=
  pIdent_.parameterMap.end();

third-party/proxygen/src/proxygen/lib/http/ProxyStatus.h

@@ -43,6 +43,7 @@ class ProxyStatus {
  ProxyStatus& setClientError(const bool isProxyError);
  ProxyStatus& setServerError(const bool isProxyError);
  ProxyStatus& setClientAddress(const std::string& clientAddr);
+ ProxyStatus& setDetails(const std::string& details);
  virtual ProxyStatus& setProxyStatusParameter(folly::StringPiece name,
  const std::string& text);