BigCommerce Specialist Needed

NOTE: We only want to work with experienced BigCommerce app developers with extensive experience on the platform, having built extensions for the BigCommerce Market place before. Your offer will not be reviewed unless you show links to BigCommerce extensions you have worked on before as reference. PROJECT: We are building a BigCommerce integration. The BigCommerce app will enable the webshop to communicate with our 3rd party service and one of the main functionalities of the app is to create a coupon through the REST API We are experiencing an issue where it doesn’t look like using the REST API allows us to specify customer groups when creating a coupon. We are not any specialists in BigCommerce, but we checked how plugins work in BigCommerce and it seems they are just 3rd party applications which in the end calls BigCommerce API. So you cannot build plugins for BC to change their functionality (for example to create our own API which could allow customer groups set)? We also investigated their GraphQL but it doesn’t look you can manage coupons from there? So we need someone who is an expert in BigCommerce and who can help us solve this particular issue with specifying a customer group when creating a coupon through the API. This project will be on an hourly rate to help us on this issue and other questions we might how while we are building completing our BC app. Look forward to hearing form you.