Shared/Removed access notifications

[KevryP]

Added functionality for notifications pertaining to the sharing or removal of access to a card set. Server side changes: Added: notification.js model route for retrieving users' notifications Modified: sharedCardset.js model to include 'revoked' in authority ENUM sharedCardset routes to exclude users with revoked access from collaborator list Client side changes: Modified: collaboratorList to update rather than delete sharedCardset entries when revoking access Notifications.js to differentiate between friend request notifications and sharedCardset notifications

To test: Log into two accounts, grantor and grantee Share access of a card set from grantor to grantee. Check for a notification on the grantee, accept that notification to remove it. On the grantor account, remove the grantee' access to the cardset On the grantee account, observe that access to the cardset has been revoked and accept the notification.

[render[bot]]

Your Render PR Server URL is https://audiocard-client-pr-174.onrender.com.

Follow its progress at https://dashboard.render.com/web/srv-coekvn4f7o1s73ckr42g.

[render[bot]]

Your Render PR Server URL is https://audiocard-server-pr-174.onrender.com.

Follow its progress at https://dashboard.render.com/web/srv-coekvo4f7o1s73ckr480.