codify "platform" into resolution logic, server-fn/fullstack overhaul (#4596)

overhaul dioxus fullstack using a new implementation of server_fn

This PR is a complete rewrite of dioxus fullstack designed to improve compatibility with axum and to fix a number of compilation errors based on feature flag unification plumbing through macros.

examples/06-routing/router_restore_scroll.rs

@@ -0,0 +1,73 @@
+use std::rc::Rc;
+
+use dioxus::html::geometry::PixelsVector2D;
+use dioxus::prelude::*;
+
+#[derive(Clone, Routable, Debug, PartialEq)]
+enum Route {
+    #[route("/")]
+    Home {},
+    #[route("/blog/:id")]
+    Blog { id: i32 },
+}
+
+fn main() {
+    dioxus::launch(App);
+}
+
+#[component]
+fn App() -> Element {
+    use_context_provider(|| Signal::new(Scroll::default()));
+
+    rsx! {
+        Router::<Route> {}
+    }
+}
+
+#[component]
+fn Blog(id: i32) -> Element {
+    rsx! {
+        GoBackButton { "Go back" }
+        div { "Blog post {id}" }
+    }
+}
+
+type Scroll = Option<PixelsVector2D>;
+
+#[component]
+fn Home() -> Element {
+    let mut element: Signal<Option<Rc<MountedData>>> = use_signal(|| None);
+    let mut scroll = use_context::<Signal<Scroll>>();
+
+    _ = use_resource(move || async move {
+        if let (Some(element), Some(scroll)) = (element.read().as_ref(), *scroll.peek()) {
+            element
+                .scroll(scroll, ScrollBehavior::Instant)
+                .await
+                .unwrap();
+        }
+    });
+
+    rsx! {
+        div {
+            height: "300px",
+            overflow_y: "auto",
+            border: "1px solid black",
+
+            onmounted: move |event| element.set(Some(event.data())),
+
+            onscroll: move |_| async move {
+                if let Some(element) = element.cloned() {
+                    scroll.set(Some(element.get_scroll_offset().await.unwrap()))
+                }
+            },
+
+            for i in 0..100 {
+                div { height: "20px",
+
+                    Link { to: Route::Blog { id: i }, "Blog {i}" }
+                }
+            }
+        }
+    }
+}