OPDS-PS v1.2 Support + a few bugfixes (#1869)

* Fixed up a localization lookup test case

* Refactored some webp to a unified method

* Cleaned up some code

* Expanded webp conversion for covers to all entities

* Code cleanup

* Prompt the user when they are about to delete multiple series via bulk actions

* Aligned Kavita to OPDS-PS 1.2.

* Fixed a bug where clearing metadata filter of series name didn't clear the actual field.

* Added some documentation

* Refactored how covert covers to webp works. Now we will handle all custom covers for all entities. Volumes and Series will not be touched but instead be updated via a RefreshCovers call. This will fix up the references much faster.

* Fixed up the OPDS-PS 1.2 attributes to only show on PS links

API/Services/Tasks/Scanner/Parser/Parser.cs

@@ -907,7 +907,7 @@ public static class Parser
 
     public static bool IsImage(string filePath)
     {
-        return !filePath.StartsWith(".") && ImageRegex.IsMatch(Path.GetExtension(filePath));
+        return !filePath.StartsWith('.') && ImageRegex.IsMatch(Path.GetExtension(filePath));
     }
 
     public static bool IsXml(string filePath)