Zendesk tickets side load objects

[guptaa3]

Description of change

Adding the functionality to side load ticket objects
https://developer.zendesk.com/documentation/ticketing/using-the-zendesk-api/side_loading/#special-sideloads

1. Added a new field "sideload-objects" that can be passed in the metadata of the catalog file as a list
2. A variable "SIDELOAD_OBJECTS" added which has a list of all objects that can be side loaded to tickets (more can be added later)
3. Method added to add the schema for these side loaded objects to stream.schema which will check if these objects are valid side load objects and add the schema if true
4. Change added to fetch tickets call to include sideload objects

Manual QA steps

• Tested by loading the side load objects
• test table can be temporarily found here in public.raw_zendesk_tickets_test_sideload (internal to twilio)

Risks

Rollback steps

• revert this branch

[BenjMaq]

Overall LGTM. Small request and small nits