Description:
    Generates a service object.

Examples:
    * Generating a service with no arguments:

        $ rails generate service ImportUsers

        # app/services/import_users.rb
        class ImportUsers
          def self.call
            new.call
          end

          def call
          end
        end

        # spec/services/import_users_spec.rb
        require "rails_helper"

        RSpec.describe ImportUsers, type: :service do
          pending "add some examples to (or delete) #{__FILE__}"
        end

    * Generating a service with arguments:

        $ rails generate service ImportUsers users

        # app/services/import_users.rb
        class ImportUsers
          def self.call(user)
            new(user).call
          end

          def initialize(user)
            @user = user
          end

          def call
          end
        end

        # spec/services/import_users_spec.rb
        # Same as above

    * Generating a namespaced service:

        $ rails generate service users/import users

        # app/services/users/import.rb
        class Users::Import
          def self.call(users)
            new(users).call
          end

          def initialize(users)
            @users = users
          end

          def call
          end
        end

        # spec/services/users/import_spec.rb
        require "rails_helper"

        RSpec.describe Users::Import, type: :service do
          pending "add some examples to (or delete) #{__FILE__}"
        end