Update Twitter shortcode oEmbed endpoint

The existing endpoint will be retired and removed on November 23, 2021.
References:

- https://twittercommunity.com/t/consolidating-the-oembed-functionality/154690
- https://developer.twitter.com/en/docs/twitter-for-websites/oembed-api#Embedded

This is a backward compatible change.

The existing endpoint requires a single parameter: the id of the tweet.

The new endpoint requires two parameters: the id of the tweet, and the
user with whom it is associated. For the moment, if you supply the wrong
user, the request will be redirected (with a small delay) to the correct
user/id pair. This behavior is undocumented, but we will take advantage
of it as Hugo site authors transition to the new syntax.

{{< tweet 1453110110599868418 >}} --> works, throws warning, deprecate at some point

{{< tweet user="SanDiegoZoo" id="1453110110599868418" >}} --> new syntax

Fixes #8130

tpl/tplimpl/embedded/templates/shortcodes/twitter.html

@@ -1,10 +1,35 @@
 {{- $pc := .Page.Site.Config.Privacy.Twitter -}}
 {{- if not $pc.Disable -}}
-{{- if $pc.Simple -}}
-{{ template "_internal/shortcodes/twitter_simple.html" . }}
-{{- else -}}
-{{- $url := printf "https://api.twitter.com/1/statuses/oembed.json?id=%v&dnt=%t" (index .Params 0) $pc.EnableDNT -}}
-{{- $json := getJSON $url -}}
-{{ $json.html | safeHTML }}
+  {{- if $pc.Simple -}}
+    {{- template "_internal/shortcodes/twitter_simple.html" . -}}
+  {{- else -}}
+    {{- $msg1 := "The %q shortcode requires two named parameters: user and id. See %s" -}}
+    {{- $msg2 := "The %q shortcode will soon require two named parameters: user and id. See %s" -}}
+    {{- if .IsNamedParams -}}
+      {{- $id := .Get "id" -}}
+      {{- $user := .Get "user" -}}
+      {{- if and $id $user -}}
+        {{- template "render-tweet" (dict "id" $id "user" $user "dnt" $pc.EnableDNT) -}}
+      {{- else -}}
+        {{- errorf $msg1 .Name .Position -}}
+      {{- end -}}
+    {{- else -}}
+      {{- $id := .Get 1 -}}
+      {{- $user := .Get 0 -}}
+      {{- if eq 1 (len .Params) -}}
+        {{- $id = .Get 0 -}}
+        {{- $user = "x" -}} {{/* This triggers a redirect. It works, but may not work forever. */}}
+        {{- warnf $msg2 .Name .Position -}}
+      {{- end -}}
+      {{- template "render-tweet" (dict "id" $id "user" $user "dnt" $pc.EnableDNT) -}}
+    {{- end -}}
+  {{- end -}}
+{{- end -}}
+
+{{- define "render-tweet" -}}
+  {{- $url := printf "https://twitter.com/%v/status/%v" .user .id -}}
+  {{- $query := querify "url" $url "dnt" .dnt -}}
+  {{- $request := printf "https://publish.twitter.com/oembed?%s" $query -}}
+  {{- $json := getJSON $request -}}
+  {{- $json.html | safeHTML -}}
 {{- end -}}
-{{- end -}}