Community and Collection Tree fixes

[benbosman]

References

• Community and Collection Tree #505

Description

We noticed some problems with the initial Community and Collection Tree implementation. This PR:

• Refactored the service/component/datasource so the service is stateless again
• Refactored the code so it builds the list page by page, instead of retrieving all objects at once from the server when you already have a few pages
• Resolved issues with observables
• Changes the variable determining Community/Collection pagesize in tree
• Simplifies the showMore node determination
• Adjusts the Tests for the applied changes

Instructions for Reviewers

It's best to test this PR with a big community/collection tree (many root node, many child nodes)

Checklist

This checklist provides a reminder of what we are going to look for when reviewing your PR. You need not complete this checklist prior to creating your PR (draft PRs are always welcome). If you are unsure about an item in the checklist, don't hesitate to ask. We're here to help!

• My PR is small in size (e.g. less than 1,000 lines of code, not including comments & specs/tests), or I have provided reasons as to why that's not possible.
• My PR passes TSLint validation using yarn run lint
• My PR includes TypeDoc comments for all new (or modified) public methods and classes. It also includes TypeDoc for large or complex private methods.
• My PR passes all specs/tests and includes new/updated specs for any bug fixes, improvements or new features. A few reminders about what constitutes good tests:
  • Include tests for different user types (if behavior differs), including: (1) Anonymous user, (2) Logged in user (non-admin), and (3) Administrator.
  • Include tests for error scenarios, e.g. when errors/warnings should appear (or buttons should be disabled).
  • For bug fixes, include a test that reproduces the bug and proves it is fixed. For clarity, it may be useful to provide the test in a separate commit from the bug fix.
• If my PR includes new, third-party dependencies (in package.json), I've made sure their licenses align with the DSpace BSD License based on the Licensing of Contributions documentation.

[artlowel]

Thanks @benbosman

I had a few points of feedback

[artlowel]

This is likely left on 2 for testing during development. Since we want to avoid pagination inside the tree to only where it is really necessary for performance, I'd change this to at least 50

[artlowel]

Thanks @MarieVerdonck!

[tdonohue]

👍 Looks good to me too! I gave this some light testing and it all works great. Thanks @MarieVerdonck !