desktop: Handle cookies and Content-Type for HTTP requests

Both of these are handled automatically by the browser in the
web backend. This makes the desktop client store cookies between
requests (though they are discarded when the desktop player is closed),
and set the "Content-Type" header based on the mime-type supplied
in the URLRequest.

Cargo.lock

@@ -2222,6 +2222,12 @@ dependencies = [
  "itoa",
 ]
 
+[[package]]
+name = "httpdate"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df3b46402a9d5adb4c86a0cf463f42e19994e3ee891101b1841f30a545cb49a9"
+
 [[package]]
 name = "humantime"
 version = "2.1.0"
@@ -2414,6 +2420,7 @@ dependencies = [
  "event-listener",
  "futures-lite",
  "http",
+ "httpdate",
  "log",
  "mime",
  "once_cell",

desktop/Cargo.toml

@@ -26,7 +26,7 @@ webbrowser = "0.8.11"
 url = "2.4.1"
 arboard = "3.2.1"
 dirs = "5.0"
-isahc = "1.7.2"
+isahc = { version = "1.7.2", features = ["cookies"] }
 rfd = "0.12.0"
 anyhow = "1.0"
 bytemuck = "1.14.0"

desktop/src/backends/navigator.rs

@@ -70,6 +70,7 @@ impl ExternalNavigatorBackend {
         let proxy = proxy.and_then(|url| url.as_str().parse().ok());
         let builder = HttpClient::builder()
             .proxy(proxy)
+            .cookies()
             .redirect_policy(RedirectPolicy::Follow);
 
         let client = builder.build().ok().map(Rc::new);
@@ -244,6 +245,7 @@ impl NavigatorBackend for ExternalNavigatorBackend {
                     NavigationMethod::Get => IsahcRequest::get(processed_url.to_string()),
                     NavigationMethod::Post => IsahcRequest::post(processed_url.to_string()),
                 };
+                let (body_data, mime) = request.body().clone().unwrap_or_default();
                 if let Some(headers) = isahc_request.headers_mut() {
                     for (name, val) in request.headers().iter() {
                         headers.insert(
@@ -257,9 +259,15 @@ impl NavigatorBackend for ExternalNavigatorBackend {
                             })?,
                         );
                     }
+                    headers.insert(
+                        "Content-Type",
+                        HeaderValue::from_str(&mime).map_err(|e| ErrorResponse {
+                            url: processed_url.to_string(),
+                            error: Error::FetchError(e.to_string()),
+                        })?,
+                    );
                 }
 
-                let (body_data, _) = request.body().clone().unwrap_or_default();
                 let body = isahc_request.body(body_data).map_err(|e| ErrorResponse {
                     url: processed_url.to_string(),
                     error: Error::FetchError(e.to_string()),