Feature: Implement multi-user access to HomeUpkeep

[mattybojo]

In order to support additional users, the code needs to be enhanced.

Current idea:

1. Add new property "friends" (or other name) to be an array of all user IDs (from firestore) that the current user wishes to share data with.
2. Inside AuthService or other common helper file, implement a standard where clause that will check for data belonging to user and any "friends" the user wants to share data between. Use the property from 1 above. This will then be imported into each service as needed.
3. All documents in firebase need to have a "user" property that will be the firestore ID of the user.

[mattybojo]

Reopening due to new user's ability to access add buttons on recipe-list page.

Implement route guard or some other way of blocking access to any UI functionality if the current user is not an approved/allowed user.