Use attachment description as alt text in html

Closes #805

DiscordChatExporter.Cli.Tests/Specs/HtmlWriting/AttachmentSpecs.cs

@@ -42,7 +42,7 @@ public record AttachmentSpecs(ExportWrapperFixture ExportWrapper) : IClassFixtur
             Snowflake.Parse("885654862656843786")
         );
 
-        var imageUrl = message.QuerySelector("img[alt*=\"attachment\" i]")?.GetAttribute("src");
+        var imageUrl = message.QuerySelector(".chatlog__attachment img")?.GetAttribute("src");
 
         // Assert
         message.Text().Should().Contain("Image attachment");

DiscordChatExporter.Core/Discord/Data/Attachment.cs

@@ -13,6 +13,7 @@ public partial record Attachment(
     Snowflake Id,
     string Url,
     string FileName,
+    string? Description,
     int? Width,
     int? Height,
     FileSize FileSize) : IHasId
@@ -37,8 +38,9 @@ public partial record Attachment
         var width = json.GetPropertyOrNull("width")?.GetInt32OrNull();
         var height = json.GetPropertyOrNull("height")?.GetInt32OrNull();
         var fileName = json.GetProperty("filename").GetNonNullString();
+        var description = json.GetPropertyOrNull("description")?.GetNonWhiteSpaceStringOrNull();
         var fileSize = json.GetProperty("size").GetInt64().Pipe(FileSize.FromBytes);
 
-        return new Attachment(id, url, fileName, width, height, fileSize);
+        return new Attachment(id, url, fileName, description, width, height, fileSize);
     }
 }

DiscordChatExporter.Core/Exporting/Writers/Html/MessageGroupTemplate.cshtml

@@ -158,19 +158,19 @@
                         @if (attachment.IsImage)
                         {
                             <a href="@await ResolveUrlAsync(attachment.Url)">
-                                <img class="chatlog__attachment-media" src="@await ResolveUrlAsync(attachment.Url)" alt="Image attachment" title="Image: @attachment.FileName (@attachment.FileSize)" loading="lazy">
+                                <img class="chatlog__attachment-media" src="@await ResolveUrlAsync(attachment.Url)" alt="@(attachment.Description ?? "Image attachment")" title="Image: @attachment.FileName (@attachment.FileSize)" loading="lazy">
                             </a>
                         }
                         else if (attachment.IsVideo)
                         {
                             <video class="chatlog__attachment-media" controls>
-                                <source src="@await ResolveUrlAsync(attachment.Url)" alt="Video attachment" title="Video: @attachment.FileName (@attachment.FileSize)">
+                                <source src="@await ResolveUrlAsync(attachment.Url)" alt="@(attachment.Description ?? "Video attachment")" title="Video: @attachment.FileName (@attachment.FileSize)">
                             </video>
                         }
                         else if (attachment.IsAudio)
                         {
                             <audio class="chatlog__attachment-media" controls>
-                                <source src="@await ResolveUrlAsync(attachment.Url)" alt="Audio attachment" title="Audio: @attachment.FileName (@attachment.FileSize)">
+                                <source src="@await ResolveUrlAsync(attachment.Url)" alt="@(attachment.Description ?? "Audio attachment")" title="Audio: @attachment.FileName (@attachment.FileSize)">
                             </audio>
                         }
                         else