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/08-apis/window_popup.rs

@@ -0,0 +1,70 @@
+//! This example shows how to create a popup window and send data back to the parent window.
+//! Currently Dioxus doesn't support nested renderers, hence the need to create popups as separate windows.
+
+use dioxus::prelude::*;
+use std::rc::Rc;
+
+fn main() {
+    dioxus::LaunchBuilder::desktop().launch(app);
+}
+
+fn app() -> Element {
+    let mut emails_sent = use_signal(|| Vec::new() as Vec<String>);
+
+    // Wait for responses to the compose channel, and then push them to the emails_sent signal.
+    let handle = use_coroutine(move |mut rx: UnboundedReceiver<String>| async move {
+        use futures_util::StreamExt;
+        while let Some(message) = rx.next().await {
+            emails_sent.write().push(message);
+        }
+    });
+
+    let open_compose_window = move |_evt: MouseEvent| {
+        let tx = handle.tx();
+        dioxus::desktop::window().new_window(
+            VirtualDom::new_with_props(popup, Rc::new(move |s| tx.unbounded_send(s).unwrap())),
+            Default::default(),
+        );
+    };
+
+    rsx! {
+        h1 { "This is your email" }
+        button { onclick: open_compose_window, "Click to compose a new email" }
+        ul {
+            for message in emails_sent.read().iter() {
+                li {
+                    h3 { "email" }
+                    span { "{message}" }
+                }
+            }
+        }
+    }
+}
+
+fn popup(send: Rc<dyn Fn(String)>) -> Element {
+    let mut user_input = use_signal(String::new);
+    let window = dioxus::desktop::use_window();
+
+    let close_window = move |_| {
+        println!("Attempting to close Window B");
+        window.close();
+    };
+
+    rsx! {
+        div {
+            h1 { "Compose a new email" }
+            button {
+                onclick: close_window,
+                "Close Window B (button)"
+            }
+            button {
+                onclick: move |_| {
+                    send(user_input.cloned());
+                    dioxus::desktop::window().close();
+                },
+                "Send"
+            }
+            input { oninput: move |e| user_input.set(e.value()), value: "{user_input}" }
+        }
+    }
+}