A contact is a single person that we want to interact with through messaging. In CommCareHQ, at the time of writing, contacts can either be users (CommCareUser, WebUser) or cases (CommCareCase).
In order for the messaging frameworks to interact with a contact, the contact must implement the corehq.apps.sms.mixin.CommCareMobileContactMixin.
Contacts have phone numbers which allows CommCareHQ to interact with them. All phone numbers for contacts must be stored in International Format, and the frameworks always assume a phone number is given in International Format.
Regarding the + sign before the phone number, the rule of thumb is to never store the + when storing phone numbers, and to always display it when displaying phone numbers.
A user’s phone numbers are stored as the phone_numbers attribute on the CouchUser class, which is just a list of strings.
At the time of writing, WebUsers are only allowed to have one-way phone numbers.
CommCareUsers are allowed to have two-way phone numbers, but in order to have a phone number be considered to be a two-way phone number, it must first be verified. The verification process is initiated on the edit mobile worker page and involves sending an outbound SMS to the phone number and having it be acknowledged by receiving a validated response from it.
At the time of writing, cases are allowed to have only one phone number. The following case properties are used to define a case’s phone number:
the phone number, in International Format
must be set to 1 in order to consider the phone number a two-way phone number; the point here is that the health worker registering the case should verify the phone number and the form should set this case property to 1 if the health worker has identified the phone number as verified
If two cases are registered with the same phone number and both set the verified flag to 1, it will only be granted two-way phone number status to the case who registers it first.
If a two-way phone number can be granted for the case, a corehq.apps.sms.models.PhoneNumber entry with verified set to True is created for it. This happens automatically by running celery task corehq.apps.sms.tasks.sync_case_phone_number for a case each time a case is saved.
Forcing the verification workflows before granting a phone number two-way phone number status has proven to be challenging for our users. In a (hopefully soon) future state, we will be doing away with all verification workflows and automatically consider a phone number to be a two-way phone number for the contact who registers it first.