Registers a user and creates a fundraisng profile for them and also (optionally)
creates or adds them to a team, makes a donation or registration fee.

Campaign API key authentication: When the request is authenticated with a
campaign secret key (Authorization header, Bearer raisely-sk-...) and the
explicit-user rollout is enabled for the organisation, you must supply data.user
with the registrant's details (email, firstName, lastName, password, etc.). User
fields must be nested under data.user — top-level data.firstName, data.email,
and similar fields are not read. Omitting data.user returns 400 invalid value.
The registrant may be any user (matched by email within the campaign's
organisation), including the API key owner. JWT or session authentication is
unchanged (a logged-in user may register without data.user).

If creation is successful, the response will include a token and accessToken.
However, if a user with that email already exists in the campaign, the user
will be sent an email to confirm that they want to add the profile to their account.

The records are created simultaneously in full or not at all.
If there is a problem with the donation or profile, then all records
will not be created.

The exception is for donations. If the Stripe gateway is using the PAYMENT_INTENT
method, then the donation must already be created to facilitate payment, the
donation is completed (or fails) as part of the registration.

If the registration is successful, the donation record will be assigned to the profile
once it's created.

For custom components:

RaiselyComponents.api.one('campaigns', '{campaign}').all('register').post(data = {}, params = {}, headers = {}) => Promise<{result}>

See Restie Response Data for a more detailed overview of responses through the client wrapper