Update networking layer w/ CURL and emscripten impl

External/curl-8.17.0/docs/libcurl/opts/CURLOPT_CUSTOMREQUEST.md

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+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Title: CURLOPT_CUSTOMREQUEST
+Section: 3
+Source: libcurl
+See-also:
+  - CURLINFO_EFFECTIVE_METHOD (3)
+  - CURLOPT_HTTPHEADER (3)
+  - CURLOPT_NOBODY (3)
+  - CURLOPT_REQUEST_TARGET (3)
+Protocol:
+  - HTTP
+  - FTP
+  - IMAP
+  - POP3
+  - SMTP
+Added-in: 7.1
+---
+
+# NAME
+
+CURLOPT_CUSTOMREQUEST - custom request method
+
+# SYNOPSIS
+
+~~~c
+#include <curl/curl.h>
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CUSTOMREQUEST, char *method);
+~~~
+
+# DESCRIPTION
+
+Pass a pointer to a null-terminated string as parameter.
+
+When changing the request *method* by setting CURLOPT_CUSTOMREQUEST(3), you do
+not actually change how libcurl behaves or acts: you only change the actual
+string sent in the request.
+
+libcurl passes on the verbatim string in its request without any filter or
+other safe guards. That includes white space and control characters.
+
+The application does not have to keep the string around after setting this
+option.
+
+Using this option multiple times makes the last set string override the
+previous ones. Restore to the internal default by setting this to NULL.
+
+This option can be used to specify the request:
+
+## HTTP
+
+Instead of GET or HEAD when performing HTTP based requests. This is
+particularly useful, for example, for performing an HTTP DELETE request.
+
+For example:
+
+When you tell libcurl to do a HEAD request, but then specify a GET though a
+custom request libcurl still acts as if it sent a HEAD. To switch to a proper
+HEAD use CURLOPT_NOBODY(3), to switch to a proper POST use
+CURLOPT_POST(3) or CURLOPT_POSTFIELDS(3) and to switch to a proper
+GET use CURLOPT_HTTPGET(3).
+
+Many people have wrongly used this option to replace the entire request with
+their own, including multiple headers and POST contents. While that might work
+in many cases, it might cause libcurl to send invalid requests and it could
+possibly confuse the remote server badly. Use CURLOPT_POST(3) and
+CURLOPT_POSTFIELDS(3) to set POST data. Use CURLOPT_HTTPHEADER(3) to replace
+or extend the set of headers sent by libcurl. Use CURLOPT_HTTP_VERSION(3) to
+change the HTTP version.
+
+When this option is used together with CURLOPT_FOLLOWLOCATION(3), the custom
+set method overrides the method libcurl could otherwise change to for the
+subsequent requests. You can fine-tune that decision by using the
+CURLFOLLOW_OBEYCODE bit to CURLOPT_FOLLOWLOCATION(3) to make redirects adhere
+to the redirect response code as the protocol instructs.
+
+## FTP
+
+Instead of LIST and NLST when performing FTP directory listings.
+
+## IMAP
+
+Instead of LIST when issuing IMAP based requests.
+
+## POP3
+
+Instead of LIST and RETR when issuing POP3 based requests.
+
+For example:
+
+When you tell libcurl to use a custom request it behaves like a LIST or RETR
+command was sent where it expects data to be returned by the server. As such
+CURLOPT_NOBODY(3) should be used when specifying commands such as
+**DELE** and **NOOP** for example.
+
+## SMTP
+
+Instead of a **HELP** or **VRFY** when issuing SMTP based requests.
+
+For example:
+
+Normally a multi line response is returned which can be used, in conjunction
+with CURLOPT_MAIL_RCPT(3), to specify an EXPN request. If the
+CURLOPT_NOBODY(3) option is specified then the request can be used to
+issue **NOOP** and **RSET** commands.
+
+# DEFAULT
+
+NULL
+
+# %PROTOCOLS%
+
+# EXAMPLE
+
+~~~c
+int main(void)
+{
+  CURL *curl = curl_easy_init();
+  if(curl) {
+    CURLcode res;
+    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/foo.bin");
+
+    /* DELETE the given path */
+    curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "DELETE");
+
+    res = curl_easy_perform(curl);
+
+    curl_easy_cleanup(curl);
+  }
+}
+~~~
+
+# %AVAILABILITY%
+
+# RETURN VALUE
+
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).