Allow admin to edit emails sent by Devise

custom_devise_mailer.rb

class CustomDeviseMailer < Devise::Mailer   
	def self.deliver_welcome_email(user)
		self.welcome_email(user)
	end

	def  welcome_email(user)
		@user = user
		# if the email's ID is 1
    		@welcome_email = Email.find_by_id(1)
		mail(to: @user.email, subject: "Welcome to The Pigeonhole!")
	end
end

devise.rb

Devise.setup do |config|
  config.mailer = 'CustomDeviseMailer'
end

email.rb

class Email < ActiveRecord::Base
	before_destroy :verify_indestructible
	validates_presence_of :title, :body
	
	private
	def verify_indestructible
		if indestructible?
			self.errors[:base] << "Cannot destroy this email."
			return false 
		end
	end
end

welcome_email.html.haml

- if !@welcome_email.nil? && @welcome_email.active?
	= @welcome_email.body.html_safe
- else
	%p Your default welcome email