Added support for follow-up actions

[eviljeff]

Fixes: mozilla/addons#16118

Description

Adds support for specific follow-up actions as policy enforcements, and action classes for delayed block submissions.

Context

As per the issue, this patch doesn't handle any override or appeals for these new actions. We may need to address messaging (emails) in follow-ups too. Right now the follow-up actions would be silent.

Testing

• Add one of the new enforcement follow-up actions to a policy in Cinder.
• in Cinder, moderate an add-on with that policy
• replay the webhook
• see that the normal action is enforced immediately (assuming it doesn't need to be held for 2nd level)
• and that an BlocklistSubmission instance is created, delayed for whatever amount of time the action was set to (and hard/soft as per the action)

Checklist

• Add #ISSUENUM at the top of your PR to an existing open issue in the mozilla/addons repository.
• Successfully verified the change locally.
• The change is covered by automated tests, or otherwise indicated why doing so is unnecessary/impossible.
• Add before and after screenshots (Only for changes that impact the UI).
• Add or update relevant docs reflecting the changes made.

[diox]

I noticed you added to Cinder staging:

AMO_FU_DELAY_LONG_HARD_BLOCK_ADDON	amo_fu_delay_long_hard_block_addon
AMO_FU_DELAY_LONG_SOFT_BLOCK_ADDON	amo_fu_delay_long_soft_block_addon
AMO_FU_DELAY_MID_HARD_BLOCK_ADDON	amo_fu_delay_mid_hard_block_addon
AMO_FU_DELAY_MID_SOFT_BLOCK_ADDON	amo_fu_delay_mid_soft_block_addon
AMO_FU_DELAY_SHORT_HARD_BLOCK_ADDON	amo_fu_delay_short_hard_block_addon
AMO_FU_DELAY_SHORT_SOFT_BLOCK_ADDON	amo_fu_delay_short_soft_block_addon

Should we use a more descriptive name in Cinder for the first column, and a slug with dashes instead of underscores for the second ?

[diox]

We should use constants for the 3 delays to stay consistent IMHO

[diox]

Since it will come up: we need a ticket to expose that table in Redash once it exists.