switch to a Document trait and introduce Script/Head/Style/Meta components (#2635)

* switch to a Document trait and introduce Script/Head/Style/Meta components

* Fix desktop title

* Insert special elements into the head during the inital SSR render

* Make all head component attributes optional

* hydrate head elements

* improve the server streaming head warning

* Document fullstack head hydration approach

* deduplicate head elements by href

* move Link into head::Link

* document head components

* add meta and title examples

* Fix a few doc examples

* fix formatting

* Add title to playwright tests

* serde is optional on web, but it is enabled by hydrate

* remove leftover console log

packages/fullstack/src/document/web.rs

@@ -0,0 +1,58 @@
+#![allow(unused)]
+//! On the client, we use the [`WebDocument`] implementation to render the head for any elements that were not rendered on the server.
+
+use dioxus_lib::events::Document;
+use dioxus_web::WebDocument;
+
+fn head_element_written_on_server() -> bool {
+    dioxus_web::take_server_data()
+        .ok()
+        .flatten()
+        .unwrap_or_default()
+}
+
+pub(crate) struct FullstackWebDocument;
+
+impl Document for FullstackWebDocument {
+    fn new_evaluator(
+        &self,
+        js: String,
+    ) -> generational_box::GenerationalBox<Box<dyn dioxus_lib::prelude::document::Evaluator>> {
+        WebDocument.new_evaluator(js)
+    }
+
+    fn set_title(&self, title: String) {
+        if head_element_written_on_server() {
+            return;
+        }
+        WebDocument.set_title(title);
+    }
+
+    fn create_meta(&self, props: dioxus_lib::prelude::MetaProps) {
+        if head_element_written_on_server() {
+            return;
+        }
+        WebDocument.create_meta(props);
+    }
+
+    fn create_script(&self, props: dioxus_lib::prelude::ScriptProps) {
+        if head_element_written_on_server() {
+            return;
+        }
+        WebDocument.create_script(props);
+    }
+
+    fn create_style(&self, props: dioxus_lib::prelude::StyleProps) {
+        if head_element_written_on_server() {
+            return;
+        }
+        WebDocument.create_style(props);
+    }
+
+    fn create_link(&self, props: dioxus_lib::prelude::head::LinkProps) {
+        if head_element_written_on_server() {
+            return;
+        }
+        WebDocument.create_link(props);
+    }
+}