refactor(verification): migrate verified field

[seaerchin]

Problem

Part 1 of #1522
This migrates the first /POST endpoint to the new API v3 route. This allows for us to shift our new routes to be grouped together and allows us to follow a RESTful api structure.

Solution

Shift the old endpoint to be rooted at /api/v3 and change the structure of the route so that the form id is passed as a parameter in the URL

Tests

Ported over existing tests and changed them so that the formId parameter exists on the request

Manual Test

• create a form with a verified email field. go to the public form view; enter a email and click on verify. there should be a pop-up for the otp to be entered
• create a form with a verified mobile number field. go to the public form view; enter a number and click on verify. there should be a pop-up for the otp to be entered

[karrui]

may want to inline this since this is only used in a single test. Same for the verifiable form

[seaerchin]

i didn't do this cos it'll be reused for the related endpoints in the issues @__@ if it's an issue, i can change it!

[karrui]

lgtm