Vendor Approvel Code

Hello,
Could you please tell me what code is executed when i approve a vendor? On vendor approval I need to insert the email into a newsletter campaign via their Api but i can’t find the code, i searched for hours and i found that in wc-multivendor-membership/views/wcfmvm-view-memberships-manage.php this is where the email content is stored and the view is controlled,so the actions should be in controller wc-multivendor-membership/controllers/wcfmvm-controller-memberships-manage.php but i cant find the part of the code where the email is fetched? Could you please indicate where should i put my code for inserting the email in the campaign ? Thanks in advance!!