maint: update deps

deps/curl/docs/libcurl/opts/CURLOPT_HTTPHEADER.md

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+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Title: CURLOPT_HTTPHEADER
+Section: 3
+Source: libcurl
+See-also:
+  - CURLOPT_CUSTOMREQUEST (3)
+  - CURLOPT_HEADER (3)
+  - CURLOPT_HEADEROPT (3)
+  - CURLOPT_MIMEPOST (3)
+  - CURLOPT_PROXYHEADER (3)
+  - curl_mime_init (3)
+---
+
+# NAME
+
+CURLOPT_HTTPHEADER - set of HTTP headers
+
+# SYNOPSIS
+
+~~~c
+#include <curl/curl.h>
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPHEADER,
+                          struct curl_slist *headers);
+~~~
+
+# DESCRIPTION
+
+Pass a pointer to a linked list of HTTP headers to pass to the server and/or
+proxy in your HTTP request. The same list can be used for both host and proxy
+requests!
+
+When used within an IMAP or SMTP request to upload a MIME mail, the given
+header list establishes the document-level MIME headers to prepend to the
+uploaded document described by CURLOPT_MIMEPOST(3). This does not affect
+raw mail uploads.
+
+The linked list should be a fully valid list of **struct curl_slist**
+structs properly filled in. Use curl_slist_append(3) to create the list
+and curl_slist_free_all(3) to clean up an entire list. If you add a
+header that is otherwise generated and used by libcurl internally, your added
+header is used instead. If you add a header with no content as in 'Accept:'
+(no data on the right side of the colon), the internally used header is
+disabled/removed. With this option you can add new headers, replace internal
+headers and remove internal headers. To add a header with no content (nothing
+to the right side of the colon), use the form 'name;' (note the ending
+semicolon).
+
+The headers included in the linked list **must not** be CRLF-terminated,
+because libcurl adds CRLF after each header item itself. Failure to comply
+with this might result in strange behavior. libcurl passes on the verbatim
+strings you give it, without any filter or other safe guards. That includes
+white space and control characters.
+
+The first line in an HTTP request (containing the method, usually a GET or
+POST) is not a header and cannot be replaced using this option. Only the lines
+following the request-line are headers. Adding this method line in this list
+of headers only causes your request to send an invalid header. Use
+CURLOPT_CUSTOMREQUEST(3) to change the method.
+
+When this option is passed to curl_easy_setopt(3), libcurl does not copy
+the entire list so you **must** keep it around until you no longer use this
+*handle* for a transfer before you call curl_slist_free_all(3) on
+the list.
+
+Pass a NULL to this option to reset back to no custom headers.
+
+The most commonly replaced HTTP headers have "shortcuts" in the options
+CURLOPT_COOKIE(3), CURLOPT_USERAGENT(3) and
+CURLOPT_REFERER(3). We recommend using those.
+
+There is an alternative option that sets or replaces headers only for requests
+that are sent with CONNECT to a proxy: CURLOPT_PROXYHEADER(3). Use
+CURLOPT_HEADEROPT(3) to control the behavior.
+
+# SPECIFIC HTTP HEADERS
+
+Setting some specific headers causes libcurl to act differently.
+
+## Host:
+
+The specified hostname is used for cookie matching if the cookie engine is
+also enabled for this transfer. If the request is done over HTTP/2 or HTTP/3,
+the custom hostname is instead used in the ":authority" header field and
+Host: is not sent at all over the wire.
+
+## Transfer-Encoding: chunked
+
+Tells libcurl the upload is to be done using this chunked encoding instead of
+providing the Content-Length: field in the request.
+
+# SPECIFIC MIME HEADERS
+
+When used to build a MIME email for IMAP or SMTP, the following document-level
+headers can be set to override libcurl-generated values:
+
+## Mime-Version:
+
+Tells the parser at the receiving site how to interpret the MIME framing.
+It defaults to "1.0" and should normally not be altered.
+
+## Content-Type:
+
+Indicates the document's global structure type. By default, libcurl sets it
+to "multipart/mixed", describing a document made of independent parts. When a
+MIME mail is only composed of alternative representations of the same data
+(i.e.: HTML and plain text), this header must be set to "multipart/alternative".
+In all cases the value must be of the form "multipart/*" to respect the
+document structure and may not include the "boundary=" parameter.
+
+Other specific headers that do not have a libcurl default value but are
+strongly desired by mail delivery and user agents should also be included.
+These are "From:", "To:", "Date:" and "Subject:" among others and their
+presence and value is generally checked by anti-spam utilities.
+
+# SECURITY CONCERNS
+
+By default, this option makes libcurl send the given headers in all HTTP
+requests done by this handle. You should therefore use this option with
+caution if you for example connect to the remote site using a proxy and a
+CONNECT request, you should to consider if that proxy is supposed to also get
+the headers. They may be private or otherwise sensitive to leak.
+
+Use CURLOPT_HEADEROPT(3) to make the headers only get sent to where you
+intend them to get sent.
+
+Custom headers are sent in all requests done by the easy handle, which implies
+that if you tell libcurl to follow redirects
+(CURLOPT_FOLLOWLOCATION(3)), the same set of custom headers is sent in
+the subsequent request. Redirects can of course go to other hosts and thus
+those servers get all the contents of your custom headers too.
+
+Starting in 7.58.0, libcurl specifically prevents "Authorization:" headers
+from being sent to other hosts than the first used one, unless specifically
+permitted with the CURLOPT_UNRESTRICTED_AUTH(3) option.
+
+Starting in 7.64.0, libcurl specifically prevents "Cookie:" headers from being
+sent to other hosts than the first used one, unless specifically permitted
+with the CURLOPT_UNRESTRICTED_AUTH(3) option.
+
+# DEFAULT
+
+NULL
+
+# PROTOCOLS
+
+HTTP, IMAP and SMTP
+
+# EXAMPLE
+
+~~~c
+int main(void)
+{
+  CURL *curl = curl_easy_init();
+
+  struct curl_slist *list = NULL;
+
+  if(curl) {
+    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
+
+    list = curl_slist_append(list, "Shoesize: 10");
+    list = curl_slist_append(list, "Accept:");
+
+    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, list);
+
+    curl_easy_perform(curl);
+
+    curl_slist_free_all(list); /* free the list */
+  }
+}
+~~~
+
+# AVAILABILITY
+
+As long as HTTP is enabled. Use in MIME mail added in 7.56.0.
+
+# RETURN VALUE
+
+Returns CURLE_OK if HTTP is supported, and CURLE_UNKNOWN_OPTION if not.