Well let’s start by having them
#1 – writing functional test. They should be able to write functional test that can cover the knowledge transfer explained
#2 – Writing phpdoccs to document the code. They could as well document existing swagger documentation via phpdocs with Zircote for API platform
https://github.com/zircote/swagger-php
#3 – Initiate their work through a git pull request
this will trigger a code Review policy