[v2] Add support for AssetsHandler (#1325)

* [website] Fix devserver default value doc

* [v2] Add support for AssetsHandler

AssetsHandler is a http.Handler delegate, which gets called
as a fallback for all Non-GET requests and for GET requests
for which the Assets didn’t find the file.

Known Limitations on Linux:
- All requests are GET requests
- No request headers
- No request body
- No response status code, only StatusOK will be returned
- No response headers

Known Limitations on Windows:
-  Request body is leaking memory. Seems to be a bug in
    WebView2, investigation angoing.

Most of these limitations on Linux will be fixed in the future with
adding support for Webkit2Gtk 2.36.0+.

* [v2, linux] Add response streaming support

The complete response won’t be held anymore in memory and will
be streamed to WebKit2.

Co-authored-by: Lea Anthony <lea.anthony@gmail.com>

website/docs/guides/application-development.mdx

@@ -161,6 +161,15 @@ The second, if given, will be executed in the `frontend` directory to build the
 
 If these 2 keys aren't given, then Wails does absolutely nothing with the frontend. It is only expecting that `embed.FS`.
 
+### AssetsHandler
+
+A Wails v2 app can optionally define a `http.Handler` in the `options.App`, which allows hooking into the AssetServer to
+create files on the fly or process POST/PUT requests.
+GET requests are always first handled by the `assets` FS. If the FS doesn't find the requested file the request will be
+forwarded to the `http.Handler` for serving. Any requests other than GET will be directly processed by the `AssetsHandler`
+if specified.
+It's also possible to only use the `AssetsHandler` by specifiy `nil` as the `Assets` option.
+
 ## Built in Dev Server
 
 Running `wails dev` will start the built in dev server which will start a file watcher in your project directory. By

website/docs/reference/options.mdx

@@ -30,6 +30,7 @@ func main() {
         RGBA:              &options.RGBA{R: 0, G: 0, B: 0, A: 255},
         AlwaysOnTop:       false,
         Assets:            assets,
+        AssetsHandler:     assetsHandler,
         Menu:              app.applicationMenu(),
         Logger:            nil,
         LogLevel:          logger.DEBUG,
@@ -221,6 +222,36 @@ Type: \*embed.FS
 
 The frontend assets to be used by the application. Requires an `index.html` file.
 
+### AssetsHandler
+
+Name: AssetsHandler
+
+Type: \*http.Handler
+
+The assets handler is a generic `http.Handler` which will be called for any non GET request on the assets server
+and for GET requests which can not be served from the `assets` because the file is not found.
+
+| Value                         | Win | Mac | Lin |
+| ----------------------------- | --- | --- | --- |
+| GET                           | ✅  | ✅   | ✅  |
+| POST                          | ✅  | ✅   | ❌  |
+| PUT                           | ✅  | ✅   | ❌  |
+| PATCH                         | ✅  | ✅   | ❌  |
+| DELETE                        | ✅  | ✅   | ❌  |
+| Request Headers               | ✅  | ✅   | ❌  |
+| Request Body                  | ✅  | ✅   | ❌  |
+| Request Body Streaming        | ❌  | ❌   | ❌  |
+| Response StatusCodes          | ✅  | ✅   | ❌  |
+| Response Headers              | ✅  | ✅   | ❌  |
+| Response Body                 | ✅  | ✅   | ✅  |
+| Response Body Streaming       | ❌  | ❌   | ✅  |
+
+NOTE: Linux is currently very limited due to targeting a WebKit2GTK Version < 2.36.0. In the future some features will be
+supported by the introduction of WebKit2GTK 2.36.0+ support.
+
+NOTE: When used in combination with a Frontend DevServer there might be limitations, eg. Vite serves the index.html
+on every path, that does not contain a file extension.
+
 ### Menu
 
 Name: Menu
@@ -316,7 +347,7 @@ Defines how the window should present itself at startup.
 | --------------- | --- | --- | --- |
 | Fullscreen      | ✅  | ✅   | ✅ |
 | Maximised       | ✅  | ✅   | ✅ |
-| Minimised       | ✅  |     | ✅ |
+| Minimised       | ✅  | ❌   | ✅ |
 
 ### Bind
 

website/docs/reference/project-config.mdx

@@ -20,7 +20,7 @@ The project config resides in the `wails.json` file in the project directory. Th
 	"version": "[Project config version]",
 	"outputfilename": "[The name of the binary]",
 	"debounceMS": 100, // The default time the dev server waits to reload when it detects a vhange in assets
-	"devServer": "[Address to bind the wails dev sever to. Default: http://localhost:34115]",
+	"devServer": "[Address to bind the wails dev sever to. Default: localhost:34115]",
 	"appargs": "[Arguments passed to the application in shell style when in dev mode]",
 	"runNonNativeBuildHooks": false, // Defines if build hooks should be run though they are defined for an OS other than the host OS.
 	"postBuildHooks": {