[16.0][ADD] base_tier_validation: allow comments being optional

[hbrunn]

this allows comments to be configured to be optional depending on the record being validated/rejected (the defaults are chosen such that existing definitions won't behave differently after the update)

[OCA-git-bot]

Hi @LoisRForgeFlow, some modules you are maintaining are being modified, check this out!

[toyrobot]

approve functional review

[bosd]

Looks good! I know it is not by this commit. But it is a bit confusing that the field has_comment actually means can_comment

[github-actions[bot]]

There hasn't been any activity on this pull request in the past 4 months, so it has been marked as stale and it will be closed automatically if no further activity occurs in the next 30 days. If you want this PR to never become stale, please ask a PSC member to apply the "no stale" label.

[Stephanvandenberg]

Hi,

This PR has been tested and works like a charm.