limit disk use and keep cover art aspect ratio (#502)

* use temp file pool to limit disk use

* keep aspect ratio and crop when scaling cover art for blurred background

* fix typo

ErsatzTV.Core.Tests/FFmpeg/TranscodingTests.cs

@@ -139,6 +139,7 @@ namespace ErsatzTV.Core.Tests.FFmpeg
                 new FFmpegPlaybackSettingsCalculator(),
                 new FakeStreamSelector(),
                 new Mock<IImageCache>().Object,
+                new Mock<ITempFilePool>().Object,
                 new Mock<ILogger<FFmpegProcessService>>().Object);
 
             MediaVersion v = new MediaVersion();

ErsatzTV.Core.Tests/Metadata/MovieFolderScannerTests.cs

@@ -7,6 +7,7 @@ using System.Threading.Tasks;
 using ErsatzTV.Core.Domain;
 using ErsatzTV.Core.Errors;
 using ErsatzTV.Core.FFmpeg;
+using ErsatzTV.Core.Interfaces.FFmpeg;
 using ErsatzTV.Core.Interfaces.Images;
 using ErsatzTV.Core.Interfaces.Metadata;
 using ErsatzTV.Core.Interfaces.Repositories;
@@ -603,6 +604,7 @@ namespace ErsatzTV.Core.Tests.Metadata
                     new Mock<ILibraryRepository>().Object,
                     new Mock<IMediator>().Object,
                     null,
+                    new Mock<ITempFilePool>().Object,
                     new Mock<ILogger<MovieFolderScanner>>().Object
                 );
         }