Cover Image Picking + Forwarding Headers with EPUBs (#700)

* Ensure Kavita knows about forwarding headers (fixes issue with epub urls not going through https with reverse proxy). Fixed a case where cover image selection preferred nested folders vs files in root directory.

* Fixed broken unit test

* Added bug that I fixed to the unit tests

API/Comparators/NaturalSortComparer.cs

@@ -6,6 +6,10 @@ using static System.String;
 
 namespace API.Comparators
 {
+    /// <summary>
+    /// Attempts to emulate Windows explorer sorting
+    /// </summary>
+    /// <remarks>This is not thread-safe</remarks>
     public sealed class NaturalSortComparer : IComparer<string>, IDisposable
     {
         private readonly bool _isAscending;
@@ -23,7 +27,6 @@ namespace API.Comparators
         {
             if (x == y) return 0;
 
-            // Should be fixed: Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct.
             if (!_table.TryGetValue(x ?? Empty, out var x1))
             {
                 x1 = Regex.Split(x ?? Empty, "([0-9]+)");
@@ -33,7 +36,6 @@ namespace API.Comparators
             if (!_table.TryGetValue(y ?? Empty, out var y1))
             {
                 y1 = Regex.Split(y ?? Empty, "([0-9]+)");
-                // Should be fixed: EXCEPTION: An item with the same key has already been added. Key: M:\Girls of the Wild's\Girls of the Wild's - Ep. 083 (Season 1) [LINE Webtoon].cbz
                 _table.Add(y ?? Empty, y1);
             }
 
@@ -59,6 +61,7 @@ namespace API.Comparators
                 returnVal = 0;
             }
 
+
             return _isAscending ? returnVal : -returnVal;
         }