Feature: Need for Task status listener

[charybr]

Pull Request type

• Bugfix
• Feature
• Refactoring (no functional changes, no api changes)
• Build related changes (Please run ./gradlew generateLock saveLock to refresh dependencies)
• WHOSUSING.md
• Other (please describe):

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Changes in this PR

Describe the new behavior from this PR, and why it's needed
Issue #3587

Need for Task status listener
When the status of a task changes, we need a mechanism to notify. Just like we have WorkflowStatusListener interface, we can have TaskStatusListener interface.

Alternatives considered

Describe alternative implementation you have considered

[manan164]

Hi @charybr , thanks for the contribution.
Following are my thoughts,

1. We can put only the interface and stub implementation in the main repo and the different types of implementation in the community repo.
2. Here I see when the task gets scheduled we are notifying the external system about that. However, the status update listener can be generalized for all task statuses like SCHEDULED, IN_PROGRESS, FAILED, COMPLETED etc

thoughts @v1r3n @c4lm @apanicker-nflx ?

[charybr]

Thanks very much Manan! for the response. Please find my comments inline.

Hi @charybr , thanks for the contribution. Following are my thoughts,

1. We can put only the interface and stub implementation in the main repo and the different types of implementation in the community repo.

This is correct, just like in the case of WorkStatusListener I am adding interface and stub in main repo. Implementation is in the form of Webhook module in conductor-community repo (there is a separate PR - Netflix/conductor-community#228)

2. Here I see when the task gets scheduled we are notifying the external system about that. However, the status update listener can be generalized for all task statuses like `SCHEDULED, IN_PROGRESS, FAILED, COMPLETED` etc

Soon i will add other task status listener methods.

[charybr]

Hi @manan164, added status listener methods for all other statuses. Please review.
4ff8a49
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