Epub Table of Generation fixes for Sigil (#1689)

* Fixed generating table of contents where key lookup could fail with how Sigil packs the epubs.

* Tweaked Kavita's fallback ToC generation (when one doesn't exist in the epub) to also use CoalesceKey.

* Code smells

API/DTOs/Settings/ServerSettingDTO.cs

@@ -49,11 +49,6 @@ public class ServerSettingDto
     /// </summary>
     public bool ConvertBookmarkToWebP { get; set; }
     /// <summary>
-    /// If the Swagger UI Should be exposed. Does not require authentication, but does require a JWT.
-    /// </summary>
-    [Obsolete("Being removed in v0.7 in favor of dedicated hosted api")]
-    public bool EnableSwaggerUi { get; set; }
-    /// <summary>
     /// The amount of Backups before cleanup
     /// </summary>
     /// <remarks>Value should be between 1 and 30</remarks>