Improve documentation for the fullstack crate (#2952)

* improve documentation for the fullstack server context

* Add a section about axum integration to the crate root docs

* make serve_dioxus_application accept the cfg builder directly

* remove unused server_fn module

* improve fullstack config docs

* improve documentation for the server function macro

* fix axum router extension link

* Fix doc tests

* Fix launch builder

* Remove redundant server_only inside server function

* Fix isrg config path

packages/fullstack/README.md

@@ -63,6 +63,80 @@ async fn get_meaning(of: String) -> Result<Option<u32>, ServerFnError> {
 }
 ```
 
+## Axum Integration
+
+If you have an existing Axum router or you need more control over the server, you can use the [`DioxusRouterExt`](https://docs.rs/dioxus-fullstack/0.6.0-alpha.2/dioxus_fullstack/prelude/trait.DioxusRouterExt.html) trait to integrate with your existing Axum router.
+
+First, make sure your `axum` dependency is optional and enabled by the server feature flag. Axum cannot be compiled to wasm, so if it is enabled by default, it will cause a compile error:
+
+```toml
+[dependencies]
+dioxus = { version = "*", features = ["fullstack"] }
+axum = { version = "0.7.0", optional = true }
+
+[features]
+server = ["dep:axum", "dioxus/server"]
+web = ["dioxus/web"]
+```
+
+Then we can set up dioxus with the axum server:
+
+```rust, no_run
+#![allow(non_snake_case)]
+use dioxus::prelude::*;
+
+// The entry point for the server
+#[cfg(feature = "server")]
+fn main() {
+    // Get the address the server should run on. If the CLI is running, the CLI proxies fullstack into the main address
+    // and we use the generated address the CLI gives us
+    let cli_args = dioxus_cli_config::RuntimeCLIArguments::from_cli();
+    let address = cli_args
+        .as_ref()
+        .map(|args| args.fullstack_address().address())
+        .unwrap_or_else(SocketAddr::from(([127, 0, 0, 1], 8080)));
+
+    // Set up the axum router
+    let router = axum::Router::new()
+        // You can add a dioxus application to the router with the `serve_dioxus_application` method
+        // This will add a fallback route to the router that will serve your component and server functions
+        .serve_dioxus_application(ServeConfigBuilder::default(), App);
+
+    // Finally, we can launch the server
+    let router = router.into_make_service();
+    let listener = tokio::net::TcpListener::bind(address).await.unwrap();
+    axum::serve(listener, router).await.unwrap();
+}
+
+// For any other platform, we just launch the app
+#[cfg(not(feature = "server"))]
+fn main() {
+    launch(App);
+}
+
+#[component]
+fn App() -> Element {
+    let mut meaning = use_signal(|| None);
+
+    rsx! {
+        h1 { "Meaning of life: {meaning:?}" }
+        button {
+            onclick: move |_| async move {
+                if let Ok(data) = get_meaning("life the universe and everything".into()).await {
+                    meaning.set(data);
+                }
+            },
+            "Run a server function"
+        }
+    }
+}
+
+#[server]
+async fn get_meaning(of: String) -> Result<Option<u32>, ServerFnError> {
+    Ok(of.contains("life").then(|| 42))
+}
+```
+
 ## Getting Started
 
 To get started with full stack Dioxus, check out our [getting started guide](https://dioxuslabs.com/learn/0.5/getting_started), or the [full stack examples](https://github.com/DioxusLabs/dioxus/tree/master/examples).