0.21rc1

Originally released on 2019-08-07 17:45:34+00:00 (link).

New features:

• Expose the functions to make Kopf embeddable into other apps. #156
  • Docs: https://kopf.readthedocs.io/en/latest/embedding/

Improvements:

• Terminate the operator better, with graceful period for clean shutdown. #156
• K8s-events for cluster-scoped objects are posted to the current namespace, not "default". #165
• Kopf's handler errors renamed to kopf.PermanentError/kopf.TemporaryError. #159
• Kopf's permanent/temporary errors do not dump strack-traces anymore. #159

Internal changes:

• CodeCov PR comments disabled (to prevent spamming). #170
• Some modules were moved around and split. #155