[keycloak-user] IDP Mapper Mapping User defined attribute to JWT Claim

Hello, I am using KeyCloak as IDP allowing my application to login with Google, Facebook or Linkedin I have and in-house API service which maintains certain IDs which can be looked up with Google, Facebook, Linked in usernames. I want to make these Ids available as part of the Custom JWT Claim. I want to know if I can handle this solely at IDP Mapper level without introducing any Client specific mapper. This way I can avoid replicating mappers for every client i create if I can achive it at the IDP Mapper Level itself. Please let me know Anand