potential_solution.rb

module Compliance
  module IdentityVerification
    class TestingWebhookSubdomain
      def initialize(stage, env, host)
        @stage = stage
        @host = host
        @env = env
      end

      def value
        return nil unless review_app? || @env.staging?

        subdomain
      end

      private
      
      def review_app?
        @stage.branch_staging?
      end

      def subdomain
        host.gsub('.comptoirdubitcoin.fr', '')
      end
      
    end
  end
end


# in code

  ...
  preferredLang: @customer.lg,
  custom3:       webhook_url_domain
  ...
  

def subdomain
  Compliance::IdentityVerification::TestingWebhookSubdomain.new(
    Coinhouse.stage,
    Rails.env,
    ENV['APP_HOST']
  )
end


# tests

describe '#value' do
  context 'when review-app' do
    it 'returns host subdomain'
  end

  context 'when staging' do
    it 'returns host subdomain'
  end
  
  context 'when production' do
    it 'returns nil'
  end
  context 'when development' do
    it 'returns nil'
  end
end