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/07-fullstack/through_reqwest.rs

@@ -0,0 +1,47 @@
+//! This example demonstrates that dioxus server functions can be be called directly as a Rust
+//! function or via an HTTP request using reqwest.
+//!
+//! Dioxus server functions generated a REST endpoint that can be called using any HTTP client.
+//! By default, they also support different serialization formats like JSON and CBOR. Try changing
+//! your `accept` header to see the different formats.
+
+use dioxus::prelude::*;
+
+fn main() {
+    dioxus::launch(app);
+}
+
+fn app() -> Element {
+    let mut user_from_server_fn = use_action(get_user);
+
+    let mut user_from_reqwest = use_action(move |id: i32| async move {
+        let port = dioxus::cli_config::server_port().unwrap_or(8080);
+        reqwest::get(&format!("http://localhost:{}/api/user/{}", port, id))
+            .await?
+            .json::<User>()
+            .await
+    });
+
+    rsx! {
+        button { onclick: move |_| user_from_server_fn.call(123), "Fetch Data" }
+        button { onclick: move |_| user_from_reqwest.call(456), "Fetch From Endpoint" }
+        div { display: "flex", flex_direction: "column",
+            pre { "User from server: {user_from_server_fn.value():?}", }
+            pre { "User from server: {user_from_reqwest.value():?}", }
+        }
+    }
+}
+
+#[derive(serde::Serialize, serde::Deserialize, Debug)]
+struct User {
+    id: String,
+    name: String,
+}
+
+#[get("/api/user/{id}")]
+async fn get_user(id: i32) -> Result<User> {
+    Ok(User {
+        id: id.to_string(),
+        name: "John Doe".into(),
+    })
+}