### 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_
base_redirect: str, bucket: BucketName, object_key: ObjectKey, etag: ETag
):
    """
    POST requests can redirect if successful. It will take the URL provided and append query string parameters
    (key, bucket and ETag). It needs to be a full URL.
    :param base_redirect: the URL provided for redirection
    :param bucket: bucket name
    :param object_key: object key
    :param etag: key ETag
    :return: the URL provided with the new appended query string parameters
    """
    parts = urlparser.urlparse(base_redirect)
    if not parts.netloc:
        raise ValueError("The provided URL is not valid")
    queryargs = urlparser.parse_qs(parts.query)
    queryargs["key"] = [object_key]
    queryargs["bucket"] = [bucket]
    queryargs["etag"] = [etag]
    redirect_queryargs = urlparser.urlencode(queryargs, doseq=True)
    newparts = (
        parts.scheme,
        parts.netloc,
        parts.path,
        parts.params,
        redirect_queryargs,
        parts.fragment,
    )
    return urlparser.urlunparse(newparts)
def parse_post_object_tagging_xml(tagging: str) -> Optional[dict]: