Chartmogul

- Adds support for Opportunities (https://dev.chartmogul.com/reference/opportunities)

- Fix customer website_url, add missing allow_none=True

- Add support for customer website_url

- Fix missing customer_uuid when creating a note from a customer

- Support customer notes

Added
- v4.0.0 upgrade instructions.
- Support for Python 3.12.

Removed
- Support for old pagination using `page` query params.
- Deprecated `imp` module.
- Support for Python 3.7.