Move Return reqs. pages into setup folder (#1429)

DEFRA/water-abstraction-team#126

We are on the cusp of our work to migrate the management of return versions (requirements) from NALD to WRLS going 'live'.

This is a significant feature that has seen many iterations since we started. So, before it gets used in earnest, we want to ensure it is 'ship shape and Bristol fashion'!

A crucial part of the tidy-up is moving all modules related to setting up a return version into a `/setup` subfolder, using the same pattern we used for setting up a bill run. We also move the routes to `/return-requirements/setup/{sessionId`.

This helps us distinguish pages used solely to 'set up' a new return requirement from those used to view and manage them.

app/controllers/licences.controller.js

@@ -5,7 +5,7 @@
  * @module LicencesController
  */
 
-const InitiateSessionService = require('../services/return-requirements/initiate-session.service.js')
+const InitiateSessionService = require('../services/return-requirements/setup/initiate-session.service.js')
 const LicenceSupplementaryProcessBillingFlagService = require('../services/licences/supplementary/process-billing-flag.service.js')
 const MarkedForSupplementaryBillingService = require('../services/licences/supplementary/marked-for-supplementary-billing.service.js')
 const MarkForSupplementaryBillingService = require('../services/licences/supplementary/mark-for-supplementary-billing.service.js')
@@ -50,15 +50,15 @@ async function noReturnsRequired (request, h) {
 
  const session = await InitiateSessionService.go(id, 'no-returns-required')
 
- return h.redirect(`/system/return-requirements/${session.id}/start-date`)
+ return h.redirect(`/system/return-requirements/setup/${session.id}/start-date`)
 }
 
 async function returnsRequired (request, h) {
  const { id } = request.params
 
  const session = await InitiateSessionService.go(id, 'returns-required')
 
- return h.redirect(`/system/return-requirements/${session.id}/start-date`)
+ return h.redirect(`/system/return-requirements/setup/${session.id}/start-date`)
 }
 
 async function submitMarkForSupplementaryBilling (request, h) {