fix(classifier): automatically sync drawing annotations

[eatyourgreens]

• Add an annotation.actualTask view to drawing tasks and transcription tasks.
• Add an autorun reaction which observes self.actualTask.marks for changes, and updates the annotation value.
• Remove the manual annotation.update(newValue) when a new mark is drawn.
• Rewrite annotation.toSnapshot() to use the annotation value.
• Add multiple frames to the tests.

This might be a more robust fix for problems where the classification is not updated properly after adding or removing a mark. It should keep drawing annotations in sync with their corresponding drawing tools. Whenever a drawing task's marks change, a MobX reaction updates the task's annotation.

Current behaviour, in production, is that adding a mark silently removes existing marks from the classification, except for the active frame. As a consequence, drawn marks appear to vanish from all frames in the subject viewer, except the active frame. See #5929.

Package

• lib-classifier

Linked Issue and/or Talk Post

• Fix for PR 5754 #5913 (comment)
• closes Multiframe subjects: Drawing tools only render previous marks for the active frame #5929.

How to Review

Similar to #5919, you should be able to draw marks on any frame of a subject, and those marks will still be recorded in the classification and shown on top of the subject in subsequent steps of a workflow.

For How Did We Get Here, you should be able to draw on both frames of a subject without apparently losing drawn marks in the second step of the workflow.
https://local.zooniverse.org:8080/?project=communitiesandcrowds/how-did-we-get-here&env=production

Checklist

PR Creator - Please cater the checklist to fit the review needed for your code changes.
PR Reviewer - Use the checklist during your review. Each point should be checkmarked or discussed before PR approval.

General

• Tests are passing locally and on Github
• Documentation is up to date and changelog has been updated if appropriate
• You can yarn panic && yarn bootstrap or docker-compose up --build and FEM works as expected
• FEM works in all major desktop browsers: Firefox, Chrome, Edge, Safari (Use Browserstack account as needed)
• FEM works in a mobile browser

General UX

Example Staging Project: i-fancy-cats

• All pages of a FEM project load: Home Page, Classify Page, and About Pages
• Can submit a classification
• Can sign-in and sign-out
• The component is accessible
  • Can be used with a screen reader BBC guide to VoiceOver
  • Can be used from the keyboard WebAIM guide to keyboard testing
  • It is passing accessibility checks in the storybook

Refactoring

• The PR creator has described the reason for refactoring
• The refactored component(s) continue to work as expected

[coveralls]

coverage: 79.184% (+0.004%) from 79.18%
when pulling 028c50e on eatyourgreens:refactor-drawing-annotations
into 81eb200 on zooniverse:master.

[eatyourgreens]

Bumping this so it doesn’t go stale.