feat(sms-limiting): disable sms verifications toggling

[seaerchin]

Problem

This PR addresses the edge case when the admin wishes to perform some operation on the form field but should be prohibited from doing so because their sms limit has been exceeded. This PR is dependent on #2276

Solution

The solution consists of 2 portions.

Checking if the operation should be prohibited

• this is done though a service method called shouldUpdateFormField, where the applicable scenario is checked - the field is of type Mobile and it's verifiable. When this occurs, the free sms counts used of the admin is retrieved and checked to see if the limit has been exceeded, and a Result is returned accordingly.

Preventing operation if it should be prohibited

• because the type returned in the error case is Err<some base type>, the error returned will be propagated and short-circuited, preventing the operation from taking place

Technical Choices

1. Placing of shouldUpdateFormField in controller rather than service.
   • the choice to update should be clearly visible and not abstracted by the service
   • choice to prohibit the update should be a controller level responsibility; service should just perform a single function

[karrui]

now that I'm reading this function signature again, should we make it clearer so ppl reading only the controller can understand what this function does?

Can we further split this function up so it can be extended if needed?

const shouldUpdateFormField = (...) => {
  switch (formField.fieldType) {
    case BasicField.Mobile:
      return assessMobileFieldUpdateAllowed(...)
    default:
      return okAsync(form)
}

assessMobileFieldUpdateAllowed can still be a function in this admin-form service since it's still acting on form fields.

If not, we can also move this field type check into the controller and call assessMobileFieldUpdateAllowed. This makes the pipelines clearer

[seaerchin]

i was thinking about doing the split-up but was wary about premature optimization actually HAHA now that you've raised it, i'll split it up!

[seaerchin]

done here