Implement common Logic for different databases.

- Main goal is to make the backend user friendly. 
**- Organizer/admin should be able to select database with minimal code changes/None**
- One thought is to use database if environment secrets/ URI is given in a `config.yml` file?
Example:
```yml
database:
    type: postgressql
```


Common Databases to support
- PostgresSQL
- SQL Server
- MongoDB
