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/04-managing-state/global.rs

@@ -0,0 +1,60 @@
+//! Example: Global signals and memos
+//!
+//! This example demonstrates how to use global signals and memos to share state across your app.
+//! Global signals are simply signals that live on the root of your app and are accessible from anywhere. To access a
+//! global signal, simply use its methods like a regular signal. Calls to `read` and `write` will be forwarded to the
+//! signal at the root of your app using the `static`'s address.
+
+use dioxus::prelude::*;
+
+const STYLE: Asset = asset!("/examples/assets/counter.css");
+
+static COUNT: GlobalSignal<i32> = Signal::global(|| 0);
+static DOUBLED_COUNT: GlobalMemo<i32> = Memo::global(|| COUNT() * 2);
+
+fn main() {
+    dioxus::launch(app);
+}
+
+fn app() -> Element {
+    rsx! {
+        Stylesheet { href: STYLE }
+        Increment {}
+        Decrement {}
+        Reset {}
+        Display {}
+    }
+}
+
+#[component]
+fn Increment() -> Element {
+    rsx! {
+        button { onclick: move |_| *COUNT.write() += 1, "Up high!" }
+    }
+}
+
+#[component]
+fn Decrement() -> Element {
+    rsx! {
+        button { onclick: move |_| *COUNT.write() -= 1, "Down low!" }
+    }
+}
+
+#[component]
+fn Display() -> Element {
+    rsx! {
+        p { "Count: {COUNT}" }
+        p { "Doubled: {DOUBLED_COUNT}" }
+    }
+}
+
+#[component]
+fn Reset() -> Element {
+    // Not all write methods are available on global signals since `write` requires a mutable reference. In these cases,
+    // We can simply pull out the actual signal using the signal() method.
+    let mut as_signal = use_hook(|| COUNT.resolve());
+
+    rsx! {
+        button { onclick: move |_| as_signal.set(0), "Reset" }
+    }
+}