Updates and New APIs

[shadinaif]

Change description

• Rename get_admin_users_queryset_by_email to deprecated_get_admin_users_queryset_by_email. The change was lost by mistake in the last PR

• New APIs

  def get_organization_user_by_username_or_email(username_or_email, organization, fail_if_inactive=False):
  def deprecated_is_existing_email_but_not_linked_yet(email):

Type of change

• [x] Bug fix (fixes an issue)
• [x] New feature (adds functionality)

Related issues

https://github.com/appsembler/tahoe-sites/pull/48

Checklists

Development

• [ ] Lint rules pass locally
• [ ] Application changes have been tested thoroughly
• [ ] Automated tests covering modified code pass

Security

• [ ] Security impact of change has been considered
• [ ] Code follows company security practices and guidelines

Code review

• [ ] Pull request has a descriptive title and context useful to a reviewer. Screenshots or screencasts are attached as necessary
• [ ] "Ready for review" label attached and reviewers assigned
• [ ] Changes have been reviewed by at least one other contributor
• [ ] Pull request linked to task tracker where applicable