Design - Ruby- Create CSV files as per User defined header From same data source

I am working on requirements we have data in hash around 100+ keys. we need to generate CSV file as per user-defined header with some transformation, we may end up having 100+ template Main changes will be 1) Change column name such as Fname –> First name 2) Data transformation like Full name – > First name + Last name (adding 2 column) 3) Fixing the position of a column – Fname should be at 35 positions etc.

please suggest is it possible to define declarative way or any gem available. Can you let me know any design pattern we can apply here?

Thanks for help