feat(parameters): Allow settings boto3.client() arguments

**Is your feature request related to a problem? Please describe.**
I'm using VPC endpoints with private DNS disabled, so I have to pass `endpoint_url` to `boto3.client` to use the endpoint-specific host name. I am not able to use `parameters` because this is not supported.

**Describe the solution you'd like**
Perhaps allowing to pass additional keyword arguments to the `client` method.

