rename table users to credentials
add credentialable polymorphic foreign key
remove type column from credentials
rename User to Credential
devise for Credential
add devise gem
rails generate devise:install
rename table carer_profiles_to_carers
rename table operator_profiles to operators
rename table manager_profiles to managers
remove -profile models
clear relations to profiles
create table supervisors
create new table administrators
association between credential and roles
build association between hospital and carers and operators
join table for hospitals and managers
build association between hospitals and managers
adjust the table orders
association between manager/operator and orders