Fix Hex encoding of assets file digests

Cargo.lock

@@ -588,6 +588,7 @@ dependencies = [
  "clap",
  "digest 0.11.0-rc.4",
  "env_logger",
+ "hex",
  "httpdate",
  "include_dir",
  "jwt-simple",

Cargo.toml

@@ -41,3 +41,4 @@ lazy_static = "1.5.0"
 mailchecker = "6.0.19"
 httpdate = "1.0.3"
 build-time = "0.1.3"
+hex = "0.4.3"

src/controllers/assets_controller.rs

@@ -22,7 +22,7 @@ pub async fn assets_route(req: HttpRequest, path: web::Path<String>) -> HttpResp
         None => HttpResponse::NotFound().body("404 Not found"),
         Some(file) => {
             let res = mime_guess::from_path(path).first_or_octet_stream();
-            let digest = format!("{:x?}", sha256(file.contents()));
+            let digest = hex::encode(sha256(file.contents()));
 
             // Check if the browser already knows the file by date
             if let Some(c) = req.headers().get(header::IF_MODIFIED_SINCE) {