Join an existing shopping list with token to share and edit

Description

This refactor/feature addition builds upon last week's addition of local storage functionality, token creation, and db restructuring. This Pull Request allows users to enter an existing token on the app's home page. The token is saved to localStorage and the user is shown the list associated with that token. The shopping list is stored in our Firebase DB by this unique token.

Our unique token is checked via function checkExistingToken(). If the token exists, the list is retrieved from Firebase for display and editing. If the token does not exist in our DB collection, the user is shown an error message asking to try again or create a new list.

This PR also addresses an issue from last week, removing a route check from the Home.js component and moving it to Apps.js instead (keeping all the routing in the same place).

Related Issue

closes #6

Acceptance Criteria

[ ✓ ] When the user does not already have a token in localStorage, on the onboarding/home screen, a simple form is displayed that allows the user to enter a token
[ ✓ ] Entering the token and hitting submit saves the token to localStorage, effectively giving them joint control of the list
[ ✓ ] On submit, show an error if the token does not exist
[ ✓ ] If they get an error message, allow them to try again or create a new list

Type of Changes

	Type
	:bug: Bug fix
✓	:sparkles: New feature
✓	:hammer: Refactoring
	:100: Add tests
	:link: Update dependencies
	:scroll: Docs

Updates

Before

After

_Site directed to after correct token entry (generatedtoken)

Testing Steps / QA Criteria

Start React App in your local environment
Enter an existing token to see a test list [_generatedtoken is our current test list token]
enter a random or invalid token to see error messaging and the option to generate your own token.

the-collab-lab / tcl-23-smart-shopping-list