Twilio-tap-zendesk

* Added stream agents_activity
* upgraded zenpy version to 2.0.24

* Added optional parameter for config `end_date`
* Added a check for end_date during data fetch from API
* If passed, data would be loaded for `date >= start_date and date < end_date`

* Load was failing for objects which were not present in sideload_objects list as keyerror
* Added a check to verify if object exists in sideload list

* Added a new field "sideload-objects" that can be passed in the metadata of the catalog file as a list
* A variable "SIDELOAD_OBJECTS" added which has a list of all objects that can be side loaded to tickets
* 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
* Change added to fetch tickets call to include sideload objects

* Add `default` and `description` fields to groups stream schema
* Add new stream ticket_metric_events
* Update singer-python dependency from `singer-python==5.2.1` to pipelinewise's version `pipelinewise-singer-python==1.2.0`
* Add new fields to users stream schema
* Add new fields to tickets stream schema

* This is a fork of https://github.com/singer-io/tap-zendesk v1.5.3.