Add support for signup with root level attributes

[luisrudge]

Changes

When using additionalSignUpFields, you can now use a new property called storage to determine where the field will be stored. root will save it in the root profile. anything else will save it under user_metadata. There is no default (which means it will save to user_metadata).

References

https://auth0.com/docs/api/management/v2#!/Users/patch_users_by_id

Testing

• This change adds unit test coverage

[joshcanhelp]

@luisrudge - At first glance, this looks fine but does this just automatically start saving custom signup fields to a different place? What if someone is already using the current implementation and expects that data to continue to be saved to usermeta? Isn't that breaking?

When we first started talking about this, my idea was to add a property to the signup fields JS to indicate that you want to save this to the root profile. Like so:

var options = {
  additionalSignUpFields: [{
    name: "full_name",
    root_profile_field: "full_name"
    placeholder: "Enter your full name"
  }]
}

[luisrudge]

@joshcanhelp made it opt-in per field

[damieng]

@joshcanhelp it doesn't change behavior for existing fields - right now they go to user metadata. The default for 'storage' is user metadata.

The rationale for this design was to:

1. Keep backwards compatible
2. Allow for future expansion if other alternatives to user metadata and root profile attributes are added
3. Make it clear where data is stored

(A flag or opt-in to root profile attributes tied to that name, e.g. useRootProfileAttributes - fails objective 2 and 3)

[luisrudge]

@joshcanhelp updated PR and description