Using a serial primary key as a foreign key in a second table

Hello folks, I'm an SQL novice indeed, but working on the premise
that "No question is too simple for this list" here goes:

This is just a dummy example to make the simple problem I'm trying to
solve as clear as possible. Let's say I have 2 tables: people and
companies.

Company records have a primary key "company_id" that is a serial, and
some other fields such as the company's name.

A person record is simply some text fields (like name) and a foreign
key, "company_id" which ties the person to a company. There is a
foreign key constraint on people that ensures that every person is
tied to a company which exists in the database.

I want to add a new person, "Bugs Bunny", but I know that the company
he work for, "Looney Tunes", is not in the database.

So, I want to add the company "Looney Tunes" (which is auto-assigned
a company_id value), and then extract that id value so that I can use
it in the company_id foreign key field of Bugs Bunny's person record.

What's the simple, multiple concurrent users-safe way of doing this
in postgreSQL?

That's all Folks,

Nat

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