adds rake task that creates a sign up email domain constraint

lib/tasks/sign_up_constraint.rake

@@ -0,0 +1,36 @@
+namespace :sign_up_constraint do
+  desc 'Adds email domain constraint to the users table. '\
+        'E.g: scinote.net'
+  task :email_domain, [:domain] => :environment do |_, args|
+    if args.blank? ||
+       args.empty? ||
+       args[:domain].blank?
+      puts 'Please add the email domain'
+      return
+    end
+
+    domain = args[:domain]
+    domain = domain.strip.gsub(/\./, '\\.')
+
+    ActiveRecord::Base.connection.execute(
+      "ALTER TABLE " \
+         "users " \
+      "DROP CONSTRAINT IF EXISTS email_must_be_company_email, " \
+      "ADD CONSTRAINT " \
+        "email_must_be_company_email " \
+      "CHECK ( email ~* '^[A-Za-z0-9._%-]+@#{domain}' ) " \
+      "not valid;"
+    )
+    puts "Created the following domain constraint: #{args[:domain]}"
+  end
+
+  desc 'Remove email domain constraint from the users table.'
+  task remove_domain: :environment do
+    ActiveRecord::Base.connection.execute(
+      'ALTER TABLE ' \
+         'users ' \
+      'DROP CONSTRAINT IF EXISTS email_must_be_company_email; '
+    )
+    puts 'Email constraint has been removed'
+  end
+end