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/09-reference/optional_props.rs

@@ -0,0 +1,72 @@
+//! Optional props
+//!
+//! This example demonstrates how to use optional props in your components. The `Button` component has several props,
+//! and we use a variety of attributes to set them.
+
+use dioxus::prelude::*;
+
+fn main() {
+    dioxus::launch(app);
+}
+
+fn app() -> Element {
+    rsx! {
+        // We can set some of the props, and the rest will be filled with their default values
+        // By default `c` can take a `None` value, but `d` is required to wrap a `Some` value
+        Button {
+            a: "asd".to_string(),
+            // b can be omitted, and it will be filled with its default value
+            c: "asd".to_string(),
+            d: Some("asd".to_string()),
+            e: Some("asd".to_string()),
+        }
+
+        Button {
+            a: "asd".to_string(),
+            b: "asd".to_string(),
+
+            // We can omit the `Some` on `c` since Dioxus automatically transforms Option<T> into optional
+            c: "asd".to_string(),
+            d: Some("asd".to_string()),
+            e: "asd".to_string(),
+        }
+
+        // `b` and `e` are omitted
+        Button {
+            a: "asd".to_string(),
+            c: "asd".to_string(),
+            d: Some("asd".to_string()),
+        }
+    }
+}
+
+#[derive(Props, PartialEq, Clone)]
+struct ButtonProps {
+    a: String,
+
+    #[props(default)]
+    b: String,
+
+    c: Option<String>,
+
+    #[props(!optional)]
+    d: Option<String>,
+
+    #[props(optional)]
+    e: SthElse<String>,
+}
+
+type SthElse<T> = Option<T>;
+
+#[allow(non_snake_case)]
+fn Button(props: ButtonProps) -> Element {
+    rsx! {
+        button {
+            "{props.a} | "
+            "{props.b:?} | "
+            "{props.c:?} | "
+            "{props.d:?} | "
+            "{props.e:?}"
+        }
+    }
+}