Rename "cooldown" to "backoff" for handler retrying

[nolar]

Fix a terminology issue, but keep it backward compatible.

Issue : #222, #16

Description

Due to my not so good English vocabulary, a slightly inappropriate word was used for the delay between retries of the handlers in #222: "cooldown".

"Cooldowns" are used in the RPG games for the spells. In Computer Science, the proper word would be "backoff":

• exponential backoff,
• retry library's backoff= kwarg,
• Kubernetes pods' CrashLoopBackOff,
• Kubernetes jobs' spec.backoffLimit,
• etc.

It is better to fix this terminology issue before it spreads all over the codebase. (It is also possible that this kwarg will be extended to "exponential backoff" in the future.)

The handlers'/decorators' cooldown= kwarg and .cooldown read-only property are kept there for backward compatibility as aliases for backoff=/.backoff — since there was at least one public release with this naming (we do not know if it is already used somewhere or not).

The aliases are tested only to minimally guarantee that they work as expected until they are removed in the next major release (1.0). The rest of the tests are switched to the proper name.

Types of Changes

• Refactor/improvements

Review

List of tasks the reviewer must do to review the PR

• Tests
• Documentation

[zincr]

🤖 zincr found 0 problems , 2 warnings

ℹ️ Large Commits
ℹ️ Dependency Licensing
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Details on how to resolve are provided below

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Large Commits

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This file contains a substantial change, please review to determine if the change comes from an external source and if there are any copyright or licensing issues to be aware of

• ℹ️ tests/registries/test_decorators_deprecated_cooldown.py had +100 lines of code changed in a single commit
  Please review this file to determine the source of this change
   

Dependency Licensing

All dependencies specified in package manager files must be reviewed, banned dependency licenses will block the merge, all new dependencies introduced in this pull request will give a warning, but not block the merge

Please ensure that only dependencies with licenses compatible with the license of this project is included in the pull request.

• ℹ️ Could not process requirements.txt for new dependencies
   

[zincr]

🤖 zincr found 1 problem , 2 warnings

❌ Approvals
ℹ️ Large Commits
ℹ️ Dependency Licensing
✅ Specification

Details on how to resolve are provided below

---

Approvals

All proposed changes must be reviewed by project maintainers before they can be merged

Not enough people have approved this pull request - please ensure that 1 additional user, who have not contributed to this pull request approve the changes.

• ✅ Approved by PR author @nolar
• ❌ 1 additional approval needed
   

Large Commits

Checks all commits for large additions to a single file. Large commits should be reviewed more carefully for potential copyright and licensing issues

This file contains a substantial change, please review to determine if the change comes from an external source and if there are any copyright or licensing issues to be aware of

• ℹ️ tests/registries/test_decorators_deprecated_cooldown.py had +100 lines of code changed in a single commit
  Please review this file to determine the source of this change
   

Dependency Licensing

All dependencies specified in package manager files must be reviewed, banned dependency licenses will block the merge, all new dependencies introduced in this pull request will give a warning, but not block the merge

Please ensure that only dependencies with licenses compatible with the license of this project is included in the pull request.

• ℹ️ Could not process requirements.txt for new dependencies
   

[samurang87]

RPG's FTW