Refactor LLMS_Engagements

[thomasplevy]

Description

Refactors a significant portion of certificate and engagement related code, deprecates a lot of code and simplifies the process of generating earned certificates and achievements.

• Fixes delayed engagements may still fire after engagement has been deleted #290
• Fixes Fix spelling error in LLMS_Database_Query abstract method preprare_query() #859
• Closes Add utility function for escaping and quoting a string. #1027
• Closes Update default images #1081
• Closes Reduce code redundancy of code shared between certificates and achievements #1082
• Fixes Certificate {first_name} merge code fallback to user nickname is confusing #1640
• includes Allow editing earned certificates and achievements #1838
• See also Engagement refactoring w awarding #1845, Engagement images and more #1846, Awards query #1859

TODO

• Write achievement tests (there aren't any or possibly any)
• Replace metadata with post thumbnail for both post types (deprecate the meta properties how certificate title is deprecated)
• Deprecate achievement title & content like certificate title is deprecated
• Add extra metadata to achievements (related, engagement, etc...)
• Is certificate content properly / fully transitioned from metadata to the post content?
• Rewrite queries on the LLMS_Student model to use a WP_Query. We might have to deprecate the existing methods and create new ones, I haven't looked at this too thoroughly yet. Possibly create custom class for this, like LLMS_Engagements_Query
• Deprecate the LLMS_Achievments::trigger_engagement() class (like certificates has been deprecated)
• More tests... I wrote a lot, there's more to write.
• Do realtime testing as a user
• Did I break e2e tests completely?
• Merge this into Allow editing earned certificates and achievements #1838 or merge that into this
• Gather deprecations and write to changelog/s
• Write and test database migrations (my_cert and my_achievement) post/meta data
  • postmeta title & content => post title & content
  • Featured image meta => thumbnail
  • store user as post_author
  • store template as post_parent
  • maybe more?
• Update achievements metabox to remove (deprecated) image (@eri-trabiccolo)

How has this been tested?

• New tests
• Existing tests
• Manually (various tests with delayed & immediate engagments for emails, achievements, and certs)

Screenshots

Types of changes

• Bug fix
• Refactor existing code

Checklist:

• My code has been tested.
• My code passes all existing automated tests.
• My code follows the LifterLMS Coding & Documentation Standards.

[eri-trabiccolo]

I think it's overall good.
Although I think we should avoid sending delayed engagements when the related post has been trashed/deleted, and when the engagement status is not publish.

[eri-trabiccolo]

let's remember to modify this doc:
https://lifterlms.com/docs/enable-engagement-debug-logging/

[eri-trabiccolo]

Looks good, although, and sorry for being nitpick, I think we still miss this part:

what do we do when the related post (course/lesson/access plan etc.) is trashed/deleted?
I'd say that we should unschedule the engagement as well, although I guess we don't have a way to determine what's the scheduled action to unschedule though...

We could, when processing the delayed engagements, at least avoid the certificates/achievements to be earned if the related post doesn't exist anymore. What do you think?

Right?

And I think we should check also that the engagement type is publish, I mean the achievement/email/certificate template actually exist and is publish otherwise what do we "send" (we might end up producing a fatal btw)?

[thomasplevy]

@eri-trabiccolo, forgive me for what I have done.