### 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_
"""
    Determines if the request is targeting S3 with virtual host addressing
    :param headers: the request headers
    :return: if the request targets S3 with virtual host addressing, returns the bucket name else None
    """
    host = headers.get("host", "")
    
    if ".s3." in host and (
        (match := _s3_virtual_host_regex.match(host)) and (bucket_name := match.group("bucket"))
    ):
        return bucket_name
def get_class_attrs_from_spec_class(spec_class: Type[str]) -> set[str]:
    return {getattr(spec_class, attr) for attr in vars(spec_class) if not attr.startswith("__")}
def get_system_metadata_from_request(request: dict) -> Metadata:
    metadata: Metadata = {}
    for system_metadata_field in SYSTEM_METADATA_SETTABLE_HEADERS:
        if field_value := request.get(system_metadata_field):
            metadata[system_metadata_field] = field_value
    return metadata
def forwarded_from_virtual_host_addressed_request(headers: dict[str, str]) -> bool:
    """
    Determines if the request was forwarded from a v-host addressing style into a path one
    """
    
    
    return S3_VIRTUAL_HOST_FORWARDED_HEADER in headers
def extract_bucket_name_and_key_from_headers_and_path(