```ruby
# frozen_string_literal: true

require 'faraday'
require 'faraday_middleware'
require 'faraday/detailed_logger'
require 'cloudflair/error/cloudflair_error'

module Cloudflair
  class Connection
    def self.new
      config = Cloudflair.config
      new_faraday_from config
    end

    def self.headers
      {}.tap do |request_headers|
        cloudflare_auth_config = Cloudflair.config.cloudflare.auth

        if !(cloudflare_auth_config.key.nil? || cloudflare_auth_config.email.nil?)
          request_headers['X-Auth-Key']   = cloudflare_auth_config.key
          request_headers['X-Auth-Email'] = cloudflare_auth_config.email
        elsif !cloudflare_auth_config.user_service_key.nil?
          request_headers['Authorization'] = "Bearer #{cloudflare_auth_config.user_service_key}"
        else
          raise CloudflairError, 'Neither email & key nor user_service_key have been defined.'
        end
      end
    end

    private_class_method def self.new_faraday_from(config)
      Faraday.new(url: config.cloudflare.api_base_url, headers: headers) do |faraday|
        faraday.request :json
        faraday.response config.faraday.logger if config.faraday.logger
        faraday.response :json, content_type: /\bjson$/

        faraday.adapter config.faraday.adapter || Faraday.default_adapter
      end
    end
  end
end
```

Address PR comments and use more guard-clause-like structure.
user
```ruby
# frozen_string_literal: true

require 'faraday'
require 'faraday_middleware'
require 'faraday/detailed_logger'
require 'cloudflair/error/cloudflair_error'

module Cloudflair
  class Connection
    def self.new
      config = Cloudflair.config
      new_faraday_from config
    end

    def self.headers # rubocop:disable Metrics/AbcSize, Metrics/MethodLength
      cloudflare_auth_config = Cloudflair.config.cloudflare.auth

      if !cloudflare_auth_config.key.nil? && !cloudflare_auth_config.email.nil?
        return({
          'X-Auth-Key'   => cloudflare_auth_config.key,
          'X-Auth-Email' => cloudflare_auth_config.email
        })
      end

      unless cloudflare_auth_config.user_service_key.nil?
        return({
          'Authorization' => "Bearer #{cloudflare_auth_config.user_service_key}"
        })
      end

      raise(
        CloudflairError,
        'Neither email & key nor user_service_key have been defined.'
      )
    end

    private_class_method def self.new_faraday_from(config) # rubocop:disable Metrics/AbcSize
      Faraday.new(url: config.cloudflare.api_base_url, headers: headers) do |faraday|
        faraday.request :json
        faraday.response config.faraday.logger if config.faraday.logger
        faraday.response :json, content_type: /\bjson$/

        faraday.adapter config.faraday.adapter || Faraday.default_adapter
      end
    end
  end
end
```
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