Implement Folder config entity

I added the uiLibrary property in the issue summary which will allow us to track which part of the XB UI the folder belongs to. Note that we also need to be able to have folders under Code, but Code is not something that \Drupal\experience_builder\Entity\Component::computeUiLibrary is aware of.

Parent issue is already tracked as a stable blocker.

We previously had code in the MR that ensured that folder names are unique within a UI library. Then I asked for removing it because the concept of UI libraries is going away. What I didn't consider was that we still need unique folder names for components in the library vs. internal code components (which will eventually move to a separate menu item). I'm really sorry, but we'll need to bring back some of that code. I think we shouldn't call the property uiLibrary as that concept will still go away. Maybe parent? Any other ideas?

Another thing just occurred to me. Yes, I'm sorry. I don't anticipate more changes, fwiw. 🙂

We need to support organizing pattern entities, too, not just components. So I recommend that we rename the components property to items.

In case it's helpful for additional testsl:

I'm working on the F.E. implementation of this and added 3 test modules that create setup content

• xb_internal_code_components creates several internal code components
• xb_test_patterns creates several patterns (that are essentially the same but with different names)
• xb_test_folders creates at least two folders for patterns, library components and internal code components. It depends on the modules above + xb_test_sdc

Very nice work, this was a pleasantly solid MR to review! 😄

At the MR level, this looks near perfect, but if I zoom out to the full scope of XB, I see some concerns.

Review

1. The issue summary should be updated to explain the revised scope, because the MR was thoroughly confusing to read given the issue summary talks ONLY about components, but the MR also supports creating folders of patterns 🙃. Apparently this pivot happened in #15. (Please think about empowering a person reviewing this who hasn't been in any of the the in-person discussions 😅)
2. The issue summary should be updated to point the bullets delayed to #3541364: Delete folders to #3541364. 🙏
3. This is a new config entity type in XB, hence it needs its own new section in docs/config-management.md
4. Various smaller (e.g. test coverage, methods with a single test user …) and bigger (not using config entities' native uuid property) on the MR.

Nice progress, the BE MR is getting close to ready! 👏

Review highlights:

1. Was able to simplify the "ID + UUID and must be kept in sync" situation: https://git.drupalcode.org/project/experience_builder/-/merge_requests/1...
2. Guaranteed a consistent config export order: https://git.drupalcode.org/project/experience_builder/-/merge_requests/1...
3. Thanks to tightening test coverage, I discovered we're missing a uniqueness validator (to prevent duplication), fixed in https://git.drupalcode.org/project/experience_builder/-/merge_requests/1...
4. Missing update path test coverage: https://git.drupalcode.org/project/experience_builder/-/merge_requests/1...
5. We should be able to modify status via the HTTP API, and shouldn't have to call logic available only in PHP when testing the HTTP API: https://git.drupalcode.org/project/experience_builder/-/merge_requests/1...

Over to Felix for the last 2! 😄

🚨 Just realized something (having just finished ensuring items in a folder are unique): shouldn't we also verify that each item can only be placed in one Folder?!

It seems a usability nightmare to see the same Component appear in multiple folders in the left sidebar? 🤔 Or … perhaps … that's actually the very intent? In any case: that's currently allowed, so we should expand test coverage for that, too, arguably.

Although, that means that in order to move a Component from one Folder to another would require first deleting it from one and then adding it to another. So perhaps keeping this as-is is reasonable, and can be considered a Feature™️? 😅

Update path test looks good! 😄

Remaining:

1. #20.5 (status)
2. docs (docs/config-management.md)
3. checking item uniqueness (discussed with Felix in private chat — we realized that it's currently possible for one item to appear in multiple folders 😅)

Everything in #22 has been addressed!

Two last remarks:

1. I don't think ::loadByItemAndType() should return an array https://git.drupalcode.org/project/experience_builder/-/merge_requests/1...
2. One bit of missing test coverage in testOneFolderPerItemLimitConstraintValidation(): https://git.drupalcode.org/project/experience_builder/-/merge_requests/1...
3. Nit: https://git.drupalcode.org/project/experience_builder/-/merge_requests/1...