Add custom capabilities for story post type

[swissspidy]

Summary

Adds custom capabilities for story post type to allow for more granular control.

Relevant Technical Choices

• Adds capabilities to default user roles upon plugin activation and during database upgrade.

To-do

User-facing changes

N/A

Testing Instructions

---

Fixes #3262

[codecov]

Codecov Report

Merging #3507 into main will decrease coverage by 0.29%.
The diff coverage is 93.75%.

@@            Coverage Diff             @@
##             main    #3507      +/-   ##
==========================================
- Coverage   83.53%   83.24%   -0.30%     
==========================================
  Files         778      778              
  Lines       13459    13487      +28     
==========================================
- Hits        11243    11227      -16     
- Misses       2216     2260      +44     

Flag	Coverage Δ
#karmatests	67.50% <ø> (+0.02%)	⬆️
#unittests	66.81% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
includes/REST_API/Fonts_Controller.php	45.97% <0.00%> (ø)
includes/Story_Post_Type.php	79.53% <96.00%> (+2.16%)	⬆️
includes/Dashboard.php	23.58% <100.00%> (-35.85%)	⬇️
includes/Database_Upgrader.php	93.67% <100.00%> (+0.24%)	⬆️
includes/REST_API/Embed_Controller.php	82.02% <100.00%> (ø)
includes/REST_API/Link_Controller.php	93.42% <100.00%> (ø)
includes/Traits/Assets.php	72.41% <0.00%> (-27.59%)	⬇️
...ibrary/panes/media/common/paginatedMediaGallery.js	88.63% <0.00%> (+2.27%)	⬆️
...s/src/edit-story/elements/media/useAverageColor.js	92.85% <0.00%> (+14.28%)	⬆️

[spacedmonkey]

All the places that reference edit_posts will also need to be changed. see https://github.com/google/web-stories-wp/search?q=edit_posts&type=

[swissspidy]

@spacedmonkey Good point regarding updating occurrences of edit_posts 👍 Will add that.

Besides that, I think I should add some E2E tests here to verify the behavior for the various user roles... WDYT?

[spacedmonkey]

Besides that, I think I should add some E2E tests here to verify the behavior for the various user roles... WDYT?

Should all tests run in different user roles like how gutenberg e2e works? Some tests could be skip for some roles.

[swissspidy]

Should all tests run in different user roles like how gutenberg e2e works? Some tests could be skip for some roles.

That's no longer accurate. Gutenberg used to run all tests twice, once for authors, once for admins. No other roles. However, that got broken once, and author tests were removed entirely in WordPress/gutenberg#23588. They want to have more targeted author tests in the future.

There's no point in running the whole test suite N times for N roles, and then skipping the majority of tests because the role doesn't have many capabilities anyway.

More targeted tests are more useful, tests/e2e/specs/editor/authorUser.js is an example of that.

Similarly, we could have a contributorUser.js test that verifies that users cannot access most of the plugin. (Just thinking out loud here)

NB, one cannot easily programmatically skip tests with Jest anyway, see jestjs/jest#7245

[spacedmonkey]

So the last two things,

• adding on action when adding roles.
• Change references of edit_posts

[spacedmonkey]

Notice an issue.

[spacedmonkey]

LGTM