```ruby
module Ci
  module API
    # Runners API
    class Runners < Grape::API
      resource :runners do
        # Delete runner
        # Parameters:
        #   token (required) - The unique token of runner
        #
        # Example Request:
        #   GET /runners/delete
        delete "delete" do
          required_attributes! [:token]
          authenticate_runner!
          Ci::Runner.find_by_token(params[:token]).destroy
        end

        # Register a new runner
        #
        # Note: This is an "internal" API called when setting up
        # runners, so it is authenticated differently.
        #
        # Parameters:
        #   token (required) - The unique token of runner
        #
        # Example Request:
        #   POST /runners/register
        post "register" do
          required_attributes! [:token]

          attributes = { description: params[:description],
                         tag_list: params[:tag_list],
                         run_untagged: params[:run_untagged] || true }

          runner =
            if runner_registration_token_valid?
              # Create shared runner. Requires admin access
              Ci::Runner.create(attributes.merge(is_shared: true))
            elsif project = Project.find_by(runners_token: params[:token])
              # Create a specific runner for project.
              project.runners.create(attributes)
            end

          return forbidden! unless runner

          if runner.id
            runner.update(get_runner_version_from_params)
            present runner, with: Entities::Runner
          else
            not_found!
          end
        end
      end
    end
  end
end
```

Improve setting default runner attrs when using API
user
```ruby
module Ci
  module API
    # Runners API
    class Runners < Grape::API
      resource :runners do
        # Delete runner
        # Parameters:
        #   token (required) - The unique token of runner
        #
        # Example Request:
        #   GET /runners/delete
        delete "delete" do
          required_attributes! [:token]
          authenticate_runner!
          Ci::Runner.find_by_token(params[:token]).destroy
        end

        # Register a new runner
        #
        # Note: This is an "internal" API called when setting up
        # runners, so it is authenticated differently.
        #
        # Parameters:
        #   token (required) - The unique token of runner
        #
        # Example Request:
        #   POST /runners/register
        post "register" do
          required_attributes! [:token]

          attributes = { description: params[:description],
                         tag_list: params[:tag_list] }

          unless params[:run_untagged].nil?
            attributes.merge!(run_untagged: params[:run_untagged])
          end

          runner =
            if runner_registration_token_valid?
              # Create shared runner. Requires admin access
              Ci::Runner.create(attributes.merge(is_shared: true))
            elsif project = Project.find_by(runners_token: params[:token])
              # Create a specific runner for project.
              project.runners.create(attributes)
            end

          return forbidden! unless runner

          if runner.id
            runner.update(get_runner_version_from_params)
            present runner, with: Entities::Runner
          else
            not_found!
          end
        end
      end
    end
  end
end
```
assistant