Change public-facing name of "Mass/Office" to "Service"

[dchiller]

A chant's "Mass/Office" field should become "Service". (This is a user-facing change...the underlying database field need not necessarily change).

From Debra:

Here are the places I see it:
https://cantusdatabase.org/chant-search/
https://cantusdatabase.org/offices/
Terms menu drop-down
the title and the first column of https://cantusdatabase.org/offices/
on the Create Chant page: https://cantusdatabase.org/chant-create/588309 (for example)
the header here: https://cantusdatabase.org/source/588309/inventory/ (for example)

Tagging @annamorphism for any additional areas where this shows up.

We'll also need to update our own documentation about this field.

[annamorphism]

A chant has it both on view and create!
Possibly the actual description of "Unknown Office (à déterminer)" should say "service" as well, though this category is being phased out anyway I think.
It's a bit weird that the URL says /offices but leads to an explanation of "services"--do we care?

[jacobdgm]

To be consistent, I feel we should update the paths as well - /office/<id> should become /service/<id>, with all the necessary redirects set up to ensure things are backwards compatible.

It may be worth looking into changing things in the code as well, to minimize developer confusion. OfficeListView can easily be renamed ServiceListView, but I'm not sure how much trouble would arise if we renamed the model itself.