### 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,
        monkeypatch,
    ):
        # if t
        if find_spec("botocore.crt.auth"):
            # the 
            # to p
            from botocore.auth import AUTH_TYPE_MAPS, S3SigV4QueryAuth
            monkeypatch.setitem(AUTH_TYPE_MAPS, "s3v4-query", S3SigV4QueryAuth)
        key = "my-key"
        presigned_client = _s3_client_pre_signed_client(
            Config(signature_version="s3v4", s3={"payload_signing_enabled": True}),
            endpoint_url=_endpoint_url(),
        )
        def add_content_sha_header(request, **kwargs):