### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

- Localstack fails with HTTP 500, error code "InternalError", message "not enough values to unpack (expected 2, got 1)" when `CopySource` is an invalid string for `copy_object` API.

### Expected Behavior

- For the same API `copy_object`, the cloud fails with HTTP 400, error code "InvalidArgument".
- Localstack should handle invalid `CopySource` i.e., it is a dictionary with one value or an invalid string not adhering to "{bucket}/{key}" format.

### How are you starting LocalStack?

With a `docker run` command

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

    docker run localstack/localstack

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

    botoclient.copy_object(CopySource="Invalid_random_string", Bucket="test_bucket", Key=key) 


 test_bucket is a valid bucket.  

### Environment

```markdown
- OS: Ubuntu 22.04.2 LTS
- LocalStack: 2.1.0
- boto3: 1.28.6
```


### Anything else?

_No response_
# not 
            # beca
            try:
                aws_client.s3.put_bucket_website(
                    Bucket=s3_bucket,
                    WebsiteConfiguration=invalid_configuration,
                )
                assert False, f"{invalid_configuration} should have raised an exception"
            except ClientError as e:
                snapshot.match(f"invalid-website-conf-{index}", e.response)
    @markers.aws.validated
    def test_crud_website_configuration(self, s3_bucket, snapshot, aws_client):
        snapshot.add_transformer(snapshot.transform.key_value("BucketName"))
        with pytest.raises(ClientError) as e:
            aws_client.s3.get_bucket_website(Bucket=s3_bucket)
        snapshot.match("get-no-such-website-config", e.value.response)
        resp = aws_client.s3.delete_bucket_website(Bucket=s3_bucket)
        snapshot.match("del-no-such-website-config", resp)
        response = aws_client.s3.put_bucket_website(
            Bucket=s3_bucket,
            WebsiteConfiguration={"IndexDocument": {"Suffix": "index.html"}},
        )
        snapshot.match("put-website-config", response)
        response = aws_client.s3.get_bucket_website(Bucket=s3_bucket)
        snapshot.match("get-website-config", response)
        aws_client.s3.delete_bucket_website(Bucket=s3_bucket)
        with pytest.raises(ClientError):
            aws_client.s3.get_bucket_website(Bucket=s3_bucket)
    @markers.aws.validated
    def test_website_hosting_redirect_all(self, s3_create_bucket, aws_client):