### 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_
self, s3_bucket, patch_s3_skip_signature_validation_false, aws_client
    ):
        # PHP 
        # howe
        # the 
        # calc
        _key = "temp.txt"
        aws_client.s3.put_(Key=_key, Bucket=s3_bucket, Body="123")
        s3_endpoint_path_s = _endpoint_url()
        client = _s3_client_pre_signed_client(
            Config(signature_version="s3v4", s3={}),
            endpoint_url=s3_endpoint_path_s,
        )
        url = client.generate_presigned_url(
            "put_",
            Params={"Bucket": s3_bucket, "Key": _key},
        )
        parts = url.partition(s3_bucket)
        # add 
        url_f_slash = parts[0] + "%2F" + parts[1] + parts[2]
        req = .get(url_f_slash)
        request_content = xmltodict.parse(req.content)
        assert "GET\n//test-bucket" in request_content["Error"]["CanonicalRequest"]
    @pytest.mark.parametrize(
        "signature_version",
        ["s3", "s3v4"],
    )
    @markers.aws.validated
    def test_s3_presign_url_encoding(