This functionality can be utilized anytime after an application is created and before
the agreement is activated. The endpoint accepts one or more Application fields,
in keeping with the “just send what you need changed” approach outlined
in RFC 7396.

Fields which are designated nullable can accept a value of null,
which will clear any previously saved value for that field.
Outside of those fields, once data for a field is saved it cannot be cleared.

After an agreement is signed, changes to the applicant name or finance terms will not be
accepted through this endpoint, and can only be modified by creating an addendum.

Payment methods, finance terms, or other contact information cannot be updated after the
agreement has been activated. The patient, however, can update their information through
the patient portal.