Prevent cascade delete when deleting physicians

[Kupinaaa]

Deleting a physician would result in all of his dependents to be deleted, which means that all the visits that that physicians had would be deleted with it. This is unwanted behavior, I should look into flagging a physician as deleted instead, or having a dummy physician to rewire the visits to, so that they do not stay deleted. I could also make the physician foreign key nullable and then override the default delete cascading behavior of EF.