Facebook-business

Added
- `delivery_category` field to Content for Conversions API.

Added
- Added HttpServiceInterface to enable the default request object to be overridden by a user-defined HTTP Request Service object. Available for Conversions API create event requests.
- Added batching to Conversions API. Create batched event requests by using BatchProcessor.

Added
- Added partner_agent field to Conversions API EventRequest and EventRequestAsync.
- Added async support to Conversions API - Create event request promises by using EventRequestAsync.
- `lead_id` field to the Conversions API `user_data` section.

Changed
- Graph API call upgrade to [v8.0](https://developers.facebook.com/docs/graph-api/changelog/version8.0)

Fixed
- Fixed `delivery_category` field being mandatory in custom_data section for Conversions API.

Added
- `delivery_category` field in custom_data section for Conversions API(formerly Serverside API).

Added
- Added support for data processing options in Serverside API. For more details see : https://developers.facebook.com/docs/marketing-apis/data-processing-options

Fixed
- Adding Python 2.7 compatibility for ServerSide API