fix: Set Platform.Value

Author: HofmeisterAn

docs/api/create_docker_container.md

@@ -15,7 +15,7 @@ _ = new ContainerBuilder()
 
 For more advanced scenarios, `WithImage` also supports `IImage`, giving you more control over how the image is represented and its properties are resolved.
 
-If you need to target a specific platform, the `DockerImage` implementation provides an overload that lets you explicitly set the platform, such as `linux/amd64`.
+If you need to target a specific platform, the `DockerImage` implementation provides an overload that lets you explicitly set the platform, such as `linux/amd64`. By default, the container runtime uses the platform that matches the container host.
 
 ```csharp
 _ = new ContainerBuilder()
@@ -24,7 +24,7 @@ _ = new ContainerBuilder()
 
 !!!tip
 
-    A specifier has the format `<os>|<arch>|<os>/<arch>[/<variant>]`. The user can provide either the operating system or the architecture or both. For more details, [see containerd/platforms](https://github.com/containerd/platforms).
+    A specifier has the format `<os>|<arch>|<os>/<arch>[/<variant>]`. The user can provide either the operating system or the architecture or both. For more details, see [containerd/platforms](https://github.com/containerd/platforms).
 
 ## Configure container start
 

src/Testcontainers/Images/DockerfileArchive.cs

@@ -162,13 +162,13 @@ public IEnumerable<IImage> GetBaseImages()
         .ToArray();
 
       var images = fromMatches
-        .Select(match => (Arg: match.Groups[argGroup], Image: match.Groups[imageGroup]))
-        .Select(item => (Arg: ReplaceVariables(item.Arg.Value, args), Image: ReplaceVariables(item.Image.Value, args)))
+        .Select(match => (FromArgs: match.Groups[argGroup], Image: match.Groups[imageGroup]))
+        .Select(item => (FromArgs: ReplaceVariables(item.FromArgs.Value, args), Image: ReplaceVariables(item.Image.Value, args)))
         .Where(item => !item.Image.Any(char.IsUpper))
         .Where(item => !stages.Contains(item.Image))
         .Select(item =>
         {
-          var fromArgs = ParseFromArgs(item.Arg).ToDictionary(arg => arg.Name, arg => arg.Value);
+          var fromArgs = ParseFromArgs(item.FromArgs).ToDictionary(arg => arg.Name, arg => arg.Value);
           _ = fromArgs.TryGetValue("platform", out var platform);
           return new DockerImage(item.Image, new Platform(platform));
         })

src/Testcontainers/Images/Platform.cs

@@ -22,6 +22,7 @@ public readonly struct Platform
     [PublicAPI]
     public Platform(string value)
     {
+      Value = value;
     }
 
     /// <summary>