We currently have a custom-written cloud-based application for the education industry, written in PHP with a framework that we have written ourselves.
Each customers data is placed in its own database since legal requirements require that users, documents and other data be well separated from other customers' data.
We have decided that we do not wish to maintain our own code for logging in, database abstraction etc, and would like to get access to the module-based world of Drupal. However, most cms:s keep all the information in one database.
What options/possibilites do Drupal give us here?