Configure S3 client ServiceURL with AWSCredentials or RegionEndPoint

I'm trying to write an integration test for a service that uses the AmazonS3Client in order to upload files to amazon s3 buckets.
I am running an instance of localstack on http://localhost:4556
The problem I'm having is the code in the service is setting up the s3 clients the following way:

var region = RegionEndpoint.GetBySystemName(config.Region);
var client = new AmazonS3Client(awsCredentials, region);

I am able to set custom AWS Credentials using the following code:

const string ProfileName = "localstack";
            const string AccessKey = "foo";
            const string SecretKey = "goo";
            var profileOptions = new CredentialProfileOptions()
            {
                AccessKey = AccessKey,
                SecretKey = SecretKey,
            };
            var profile = new CredentialProfile(ProfileName, profileOptions);
            var file = new SharedCredentialsFile();
            file.RegisterProfile(profile);
            var profileManager = new CredentialProfileStoreChain();

            profileManager.RegisterProfile(profile);

            profileManager.TryGetProfile(ProfileName, out CredentialProfile profileResult);

            profileResult.Options.AccessKey = AccessKey;
            profileResult.Options.SecretKey = SecretKey;
            profileManager.RegisterProfile(profileResult);

Is there a way to make sure that the client that will be created will use my localstack instance as a server?

I tried looking for a way to configure the ServiceURL through the RegionEndPoint or AWSCredentials class but without any luck. I might have missed somehting.

You can see here in the documentation some more informations about how to configure your client:

https://docs.localstack.cloud/user-guide/integrations/sdks/dotnet/

There's this note:

> If you want to specify a region and credentials when creating the client, please set them as AuthenticationRegion and BasicAWSCredentials, like in this example:
>
>
>var lambdaClient = new AmazonLambdaClient(new BasicAWSCredentials("test", "test"), new AmazonLambdaConfig(
> {
> ServiceURL = "http://localhost:4566",
> AuthenticationRegion = "eu-west-1"
> }));
>
> #### Note
>
> Make sure you are setting the AuthenticationRegion and not the RegionEndpoint. Setting the RegionEndpoint to a constant like RegionEndpoint.EUWest1 will override the ServiceURL, and your request will end up against AWS.

Also, S3 is a bit specific in a sense, because of virtual host addressed buckets (as seen in this GitHub issue comment). Using the example above, you could add ForcePathStyle = true to the config to be sure to not encounter any issue.

Using your example:

var config = new AmazonS3Config(
    {
        ServiceURL = "http://localhost:4566",
        AuthenticationRegion = config.region,
        ForcePathStyle = true
    }
);
var client = new AmazonS3Client(awsCredentials, config);