Different parts of government get billed slightly differently, and
there’s differences in how much money we’re allowed to give them.
Think these numbers are right, but should be double checked.
So that we can default services to their appropriate text allowance, we
need to find out what sector they're in. So let's start collecting that
from teams as they create new services.
I think Central/Local/NHS are the right options, but these can be easily
changed if not.
Mutating dictionaries is gross and doesn’t work as you’d expect. Better
to have the function return a new dictionary instead.
Means we can be explicit that `created_by` is one of the allowed params
when updating a service.
To prevent typos and inadvertently updating something we shouldn’t,
this adds some filtering to the update_service method to make sure it
is only allowed to update certain attributes of a service.
