Taskkit

What's Changed
* make DjangoBackend.discard_tasks atomic by saryou in https://github.com/saryou/taskkit/pull/23
* add functionality to manupilate current timestamp for testing by saryou in https://github.com/saryou/taskkit/pull/24


**Full Changelog**: https://github.com/saryou/taskkit/compare/0.2.0...0.2.1

What's Changed
* resolve `RemovedInDjango51Warning` by tanagumo in https://github.com/saryou/taskkit/pull/21
* add py.typed by saryou in https://github.com/saryou/taskkit/pull/22

New Contributors
* tanagumo made their first contribution in https://github.com/saryou/taskkit/pull/21

**Full Changelog**: https://github.com/saryou/taskkit/compare/0.1.17...0.2.0

What's Changed
* Add an option not to start helper services by saryou in https://github.com/saryou/taskkit/pull/19
* adjust worker ttl and service intervals by saryou in https://github.com/saryou/taskkit/pull/20


**Full Changelog**: https://github.com/saryou/taskkit/compare/0.1.16...0.1.17

What's Changed
* drop use_old_queue option from DjangoBackend by saryou in https://github.com/saryou/taskkit/pull/17
* Feature/polling interval by saryou in https://github.com/saryou/taskkit/pull/18


**Full Changelog**: https://github.com/saryou/taskkit/compare/0.1.15...0.1.16

What's Changed
* introduce Backend.retry_task to improve performance by saryou in https://github.com/saryou/taskkit/pull/15
* improve DjangoBackend.assign_task by saryou in https://github.com/saryou/taskkit/pull/16


**Full Changelog**: https://github.com/saryou/taskkit/compare/0.1.14...0.1.15

What's Changed
* introduce new model `TaskkitTaskQueue` to improve performance by saryou in https://github.com/saryou/taskkit/pull/14


**Full Changelog**: https://github.com/saryou/taskkit/compare/0.1.13...0.1.14