Add mirror attribute to Task

[jinmannwong]

Description

Add defaults to attributes.Mirror, enforcing a default lower limit on polling time and also add attribute to Task.

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

[jinmannwong]

Thanks for the review @colonesej. I don't have permission to merge this PR so could you please do it?

[colonesej]

It seems I can't either @jinmannwong . @corentincarton probably can.