Custom keybinds, Default language per Library, and bugfixes (#4162)

Co-authored-by: Joseph Milazzo <josephmajora@gmail.com>

API/Extensions/FlurlExtensions.cs

@@ -1,13 +1,48 @@
 using System;
+using System.Linq;
+using System.Threading.Tasks;
 using Flurl.Http;
 using Kavita.Common;
 using Kavita.Common.EnvironmentInfo;
+using Microsoft.AspNetCore.StaticFiles;
 
 namespace API.Extensions;
 #nullable enable
 
 public static class FlurlExtensions
 {
+
+    private static readonly FileExtensionContentTypeProvider FileTypeProvider = new ();
+
+    /// <summary>
+    /// Makes a head request to the url, and parses the first content type header to determine the content type
+    /// </summary>
+    /// <param name="url"></param>
+    /// <returns></returns>
+    public static async Task<string?> GetFileFormatAsync(this string url)
+    {
+        var headResponse = await url.AllowHttpStatus("2xx").HeadAsync();
+
+        // TODO: Move to new Headers class after merge with progress branch
+        var contentTypeHeader = headResponse.Headers.FirstOrDefault("Content-Type");
+        if (string.IsNullOrEmpty(contentTypeHeader))
+        {
+            return null;
+        }
+
+        var contentType = contentTypeHeader.Split(";").FirstOrDefault();
+        if (string.IsNullOrEmpty(contentType))
+        {
+            return null;
+        }
+
+        // The mappings have legacy mappings like .jpe => image/jpeg. We reverse to get the newer stuff first
+        return FileTypeProvider.Mappings
+            .Reverse()
+            .FirstOrDefault(m => m.Value.Equals(contentType, StringComparison.OrdinalIgnoreCase))
+            .Key?.TrimStart('.');
+    }
+
     public static IFlurlRequest WithKavitaPlusHeaders(this string request, string license, string? anilistToken = null)
     {
         return request