How to create a mailing list in Mailchimp with Ruby on Rails

mailing_list_controller.rb

class MailingListController < ApplicationController
  def addUser
    # Setup the keys needed to access Mailchimp's API
    dc = 'us13'
    unique_id = "f1ff300381"
    url = "https://#{dc}.api.mailchimp.com/3.0/lists/#{unique_id}/members"
    api_key = "YOUR_API_KEY"

    # You need to pass the status:subscribed field to ensure the user is subscribed
    user_details = {
      email_address: params[:email_address],
      status: "subscribed",
      merge_fields: {
        FNAME: params[:fname],
        LNAME: params[:company],
        PHONE: params[:phone],
        COMPANY: params[:company],
      },
    };

    # Create a new connection using Faraday
    conn = Faraday.new(
    url: url,
    headers: {'Content-Type' => 'application/json', 'Authorization': "Bearer #{api_key}"}
  )


    response = conn.post() do |req|
      req.body = user_details.to_json
    end

    # Parse the JSON response sent back from the Mailchimp servers
    response_body = JSON.parse(response.body)

    # Check if the subscription is successful
    if response.status == 200
      render json: {
        status: response.status,
        message: "#{user_details[:email_address]} has been added to the mailing list"
      }
    else
      render json: {
        status: response.status,
        message: response_body["detail"]
      }
    end
  end

    # Accept parameters into your API
    def mailing_list_params
      params.permit(:fname, :lname, :phone, :company, :email_address)
    end
end