overwrite content-type to fix reloading bug

For some reason we'd get
"image "*.png" cannot be displayed because it contains errors"
Turns out this is due to multiple content-type headers
So we've enabled "overwriting" when adding the header.

src/handlers/serve_file.rs

@@ -131,7 +131,7 @@ pub async fn serve_file(req: &mut Request, res: &mut Response) {
                 res.add_header("X-Accel-Redirect", xsend, true).unwrap();            
 
                 // Add the header to the response, which /may/ or /may not/ be modified by the safety check
-                res.add_header("Content-Type", mimetype, false).unwrap();
+                res.add_header("Content-Type", mimetype, true).unwrap();
             
                 // Go through all the headers and print them out, just to check for now!
                 tracing::debug!("response headers: {:?}", res.headers());
@@ -148,7 +148,7 @@ pub async fn serve_file(req: &mut Request, res: &mut Response) {
                 file.send(&headers, res).await;
             
                 // Add the header to the response, which /may/ or /may not/ be modified by the safety check
-                res.add_header("Content-Type", mimetype, false).unwrap();
+                res.add_header("Content-Type", mimetype, true).unwrap();
             
                 // Go through all the headers and print them out, just to check for now!
                 tracing::debug!("response headers: {:?}", res.headers());