### 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_
"Content-Type": "application/octet-stream",
            "X-Amz-Content-Sha256": "STREAMING-AWS4-HMAC-SHA256-PAYLOAD",
            "X-Amz-Date": "20211122T191045Z",
            "X-Amz-Decoded-Content-Length": "test",  # stri
            "Content-Length": "10",
            "Connection": "Keep-Alive",
            "Expect": "100-continue",
        }
        s3_create_bucket(Bucket=bucket_name)
        presigned_client = _s3_client_pre_signed_client(
            Config(signature_version=signature_version),
            endpoint_url=_endpoint_url(),
        )
        url = presigned_client.generate_presigned_url(
            "put_",
            Params={
                "Bucket": bucket_name,
                "Key": _key,
                "ContentType": "application/octet-stream",
                "ContentMD5": content_md5,
            },
        )
        result = .put(url, data="test", headers=headers)
        assert result.status_code == 403
        if snapshotted:
            exception = xmltodict.parse(result.content)
            snapshot.match("with-decoded-content-length", exception)
        if signature_version == "s3" or not verify_signature:
            assert b"SignatureDoesNotMatch" in result.content
        # we a