add apartment to your project - active admin adapter included this code will create databases and drop them when you create accounts

README

1- add to gemfile
gem 'apartment'

2- execute
bundle install
rails g scaffold account url:string name:string phone:string email:string address:text ssn:string valid_until:date
rake db:migrate

3- replace app/models/account.rb
4- use the authorization adapter if you were using active admin
5- create the apartment.rb initializer

6- add the line below to config/application.rb
config.middleware.use 'Apartment::Elevators::FirstSubdomain'

7- modify your database.yml to use a user who can create and drop databases
8- create a new rake task db.rake to use "rake db:migrateall" to migrate all available databases


Have Fun!

account.rb

# app/models/account.rb

class Account < ActiveRecord::Base
  attr_accessible :address, :email, :name, :phone, :ssn, :url, :valid_until
  attr_readonly :url

  validates_presence_of :url, :valid_until
  validates_uniqueness_of :url
  after_create :after_create_record
  before_destroy :before_destroy_record

  def after_create_record
    Apartment::Database.create(url)
  end

  def before_destroy_record
    Apartment::Database.drop(url)
  end

  def self.current
    find_by_url(Apartment::Database.current_database)
  end

  def expired?
    valid_until < Date.today
  end

  def expire_within?(days)
    valid_until < Date.today + days
  end

  def grace?
    expired? and valid_until+7.days >= Date.today
  end

end

apartment.rb

# config/initializers/apartment.rb

Apartment.configure do |config|
  
  config.seed_after_create = true
  config.excluded_models = ['Account']
  config.default_schema = '<your default database name here>'
  
end

db.rake

# lib/tasks/db.rake

namespace :db do

  desc "migrate all databases using Apartment migrator"
  task :migrateall => :environment do

    puts "Started migration for all databases"
    dbs = Account.pluck(:url)
    puts "Found #{dbs.size} to migrate"
    dbs.each do |db| 
      puts "Migrating database #{db}..."
      Apartment::Migrator.migrate db
    end
    
    puts "Databases migrated successfully"

  end
end

OnlyAdminsAuthorization.rb

# app/models/OnlyAdminsAuthorization.rb

class OnlyAdminsAuthorization < ActiveAdmin::AuthorizationAdapter

    def authorized?(action, subject = nil)
      
      classname = (subject.is_a? Class)? subject.name : subject.class.name
      account = Account.current

      # check if expired
      if !is_root_db? and account.expired?
        if classname!='ActiveAdmin::Page'
          return false 
        elsif subject.name!='Dashboard'
          return false
        end
      end

      # if valid then show and hide depend on role and DB
      case classname
        when AdminUser.name
          user.is_admin?
        when Account.name
          is_root_db?
        else
          true
      end

    end

    def is_root_db?
      Apartment.default_schema == Apartment::Database.current_database
    end

end