[SDK-4035] Add v4 Migration Guide

[adamjmcgrath]

V4 Migration Guide

Guide to migrating from 3.x to 4.x

• General
  • Node 16 or newer is required
  • Callbacks are no longer supported
  • Response change
• Authentication API
  • Options
  • Legacy endpoints have been removed
  • Top level methods have been removed
  • Method name changes
• Management API
  • Options
  • Top level methods have been removed
  • Method name changes