Give each person their own code and tell them what it is. A plumber or electrician signs in and sees only their own jobs. Set someone to Admin (office) and they get the calendar too — then tick exactly what they may do.
Missing from this list
These people have work booked on the
calendar but are not on the list above. Put them back from here and not with
Add someone: this keeps the number the jobs already know them by, so their
bookings stay theirs to edit. Added as new people instead, the jobs would still
show their name and stop belonging to them.
Phones signed up for notifications
A person with no phone here cannot be buzzed, however the job is booked. They fix it themselves: open the app on their own phone, sign in with their code, and allow notifications when it asks.