### 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_
body = "something body \n \n\r"
        # put 
        _key = "key-by-hostname"
        aws_client.s3.put_(
            Bucket=s3_bucket,
            Key=_key,
            Body=body,
            ContentType="text/html; charset=utf-8",
        )
        url = aws_client.s3.generate_presigned_url(
            "head_", Params={"Bucket": s3_bucket, "Key": _key}
        )
        # get 
        response = .head(url, verify=False)
        assert response.headers.get("content-length") == str(len(body))
    @markers.aws.validated
    @pytest.mark.parametrize("verify_signature", (True, False))
    @markers.snapshot.skip_snapshot_verify(
        condition=is_v2_provider,
        paths=["$..ServerSideEncryption"],
    )
    def test_put_url_metadata_with_sig_s3v4(