refactor(auth.client): (5, final) extract get current logged in user service function to Typescript

[karrui]

Chain: sendOtp <--- verifyOtp <-- fetchUser <- logout <-- getUserFromLocalStorage (you are here)

Problem

This PR is part 5 (and the final part) of migrating auth.client.js to Typescript. This PR extracts out the get current logged in admin user function

Related to #2057

Solution

Breaking Changes

• Yes - this PR contains breaking changes
• No - this PR is backwards compatible

Features:

• feat(UserService): add getUserFromLocalStorage function
• ref: replace all instances of Auth.getUser with UserService equivalent
• feat: delete (now) unused auth.client.service.js

Tests

Unit tests have been written for UserService#getUserFromLocalStorage function.

Manual tests

• Open avatar dropdown. Should load current user successfully.
• Open edit contact number modal. Should load current user successfully.
• Look at Google Analytics when you have downloaded a storage mode form responses. The label should be ${params.formTitle} (${params.formId}), ${<your email>}
• In your admin form, go to the share form page. There should be a "use go link" lightbulb tooltip thingy
• Should be able to successfully view admin form page (of your form) when logged in
• Should be able to successfully view the edit form field modal successfully when logged in
• Should be able to view form dashboard successfully when logged in
• Should be able to view form settings successfully when logged in
• Should be able to view examples page successfully when logged in
• Should be able to view billing page successfully when logged in
• In an admin form page, delete the user object from localStorage.
  • Should be logged out and redirected to the login page
  • After login, should be redirected back to the admin form page where you deleted the localStorage user.