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.

packages/fullstack/src/payloads/text.rs

@@ -0,0 +1,38 @@
+use crate::{ClientResponse, FromResponse};
+use axum_core::response::{IntoResponse, Response};
+use dioxus_fullstack_core::ServerFnError;
+use send_wrapper::SendWrapper;
+use std::future::Future;
+
+/// A simple text response type.
+///
+/// The `T` parameter can be anything that converts to and from `String`, such as `Rc<str>` or `String`.
+///
+/// Unlike `Json` or plain `String`, this uses the `text/plain` content type. The `text/plain` header
+/// will be set on the request.
+pub struct Text<T>(pub T);
+
+impl<T> Text<T> {
+    /// Create a new text response.
+    pub fn new(text: T) -> Self {
+        Self(text)
+    }
+}
+
+impl<T: Into<String>> IntoResponse for Text<T> {
+    fn into_response(self) -> Response {
+        Response::builder()
+            .header("Content-Type", "text/plain; charset=utf-8")
+            .body(axum_core::body::Body::from(self.0.into()))
+            .unwrap()
+    }
+}
+
+impl<T: From<String>> FromResponse for Text<T> {
+    fn from_response(res: ClientResponse) -> impl Future<Output = Result<Self, ServerFnError>> {
+        SendWrapper::new(async move {
+            let text = res.text().await?;
+            Ok(Text::new(text.into()))
+        })
+    }
+}