### 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_
return (
                "a;chunk-signature=b5311ac60a88890e740a41e74f3d3b03179fd058b1e24bb3ab224042377c4ec9\r\n"
                f"{content}\r\n"
                "0;chunk-signature=78fae1c533e34dbaf2b83ad64ff02e4b64b7bc681ea76b6acf84acf1c48a83cb\r\n"
                f"x-amz-checksum-sha256:{checksum_value}\r\n"
                "x-amz-trailer-signature:712fb67227583c88ac32f468fc30a249cf9ceeb0d0e947ea5e5209a10b99181c\r\n\r\n"
            )
        url = f"{config.internal_service_url()}/{s3_bucket}/{_key}"
        # test 
        wrong_data = get_data(body, "wrongchecksum")
        request = .put(url, wrong_data, headers=headers, verify=False)
        assert request.status_code == 400
        assert "Value for x-amz-checksum-sha256 header is invalid." in request.text
        # asse
        with pytest.raises(ClientError):
            aws_client.s3.get_(Bucket=s3_bucket, Key=_key)
        # put 
        valid_data = get_data(body, valid_checksum)
        req = .put(url, valid_data, headers=headers, verify=False)
        assert req.ok
        # get 
        downloaded_ = aws_client.s3.get_(Bucket=s3_bucket, Key=_key)
        download_file_ = to_str(downloaded_["Body"].read())
        assert len(body) == len(str(download_file_))
        assert body == str(download_file_)
    @markers.aws.only_localstack
    def test_upload_part_chunked_newlines_valid_etag(self, s3_bucket, aws_client, region_name):