Serve plain text files (e.g. logs) as UTF-8.

src/Prowlarr.Http/Frontend/Mappers/StaticResourceMapperBase.cs

@@ -1,7 +1,9 @@
 using System;
 using System.IO;
+using System.Text;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.StaticFiles;
+using Microsoft.Net.Http.Headers;
 using NLog;
 using NzbDrone.Common.Disk;
 using NzbDrone.Common.EnvironmentInfo;
@@ -39,7 +41,10 @@ namespace Prowlarr.Http.Frontend.Mappers
                     contentType = "application/octet-stream";
                 }
 
-                return new FileStreamResult(GetContentStream(filePath), contentType);
+                return new FileStreamResult(GetContentStream(filePath), new MediaTypeHeaderValue(contentType)
+                {
+                    Encoding = contentType == "text/plain" ? Encoding.UTF8 : null
+                });
             }
 
             _logger.Warn("File {0} not found", filePath);