[feat]: Insert newly-registered users in Strapi via content API + POST req

### Description

Newly-registered members can be inserted in the Strapi DB via the content API endpoint. Create a function that is to be invoked right after BetterAuth.signIn & prisma.createMember is done

### Suggested Solution

May be good to reference: https://strapi.io/blog/a-guide-to-role-based-access-control-in-strapi
https://docs.strapi.io/cms/api/graphql
