Consolidate list remote users api

[AlexVelezLl]

Summary

Consolidates the logic of listing remote users from the user_profile and setup_wizard plugins, and migrates them to core auth so that they are accessible by multiple plugins.

There were some differences between both endpoints, and the following decisions were made to merge them:

• The setup wizard endpoint returned an object { admin, students }, while the user_profile endpoint returned a list of users. It was decided to keep the response the same as that of user_profile as it was more flexible, and in the setup wizard to make the admin, students filter on the frontend instead of the backend.
• The setup wizard endpoint returns a 403 error if there are authentication errors, but the user_profile endpoint returns a 200 code, but with an error object. The 403 error was maintained, and where it is called to the user_profile endpoint in the frontend the error handling was updated.
• The setup_wizard endpoint gets a "facility_id" param, while the user_profile endpoint gets a "facility" param. The naming of "facility_id" was preferred.
• The user_profile endpoint validated the input data, and the setup_wizard endpoint did not. It was preferred to validate it as the user_profile.

Reviewer guidance

• Check the flow of importing users as administrator of the setup wizard.
• Check the flow of changing facilities for an "on my own" user, and merging users using administrator credentials.

Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Critical and brittle code paths are covered by unit tests

PR process

• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
• If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• If this is an important user-facing change, PR or related issue has a 'changelog' label
• If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[github-actions]

Build Artifacts

Asset type	Download link
PEX file	kolibri-.pex
Windows Installer (EXE)	kolibri-0.17.0a0.dev0+git.135.g62f59408-windows-setup-unsigned.exe
Debian Package	kolibri_0.17.0a0.dev0+git.135.g62f59408-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.17.0a0.dev0+git.135.g62f59408-0.4.2.dmg
Android Package (APK)	kolibri-0.17.0a0.dev0+git.135.g62f59408-0.1.3-debug.apk
TAR file	kolibri-0.17.0a0.dev0+git.135.g62f59408.tar.gz
WHL file	kolibri-0.17.0a0.dev0+git.135.g62f59408-py2.py3-none-any.whl