Creating a template that can take data from various sources with different column names

Hi, i'm trying to create a dashboard template in which users can upload their own data and the dashboard will visualize it. I want the user to do as little as possible to get this working. Important points:

1. The dashboard should have the ability to accept data from these sources: SQL Server, CSV and Excel files. I can't seem to find how to change data source from CSV to SQL for example.
2. The users model might have different column names, which impact the dashboard visualizations. Maybe even different relationships between the tables.

Ideally, the template should have a model, which has no data, that it takes the data from. The user then uploads his data, populates the model tables with the appropriate data and the dashboard then displays the visualizations. Any tips on how to achieve this?