discourse/app/controllers/admin/embedding_controller.rb

require_dependency 'embedding'

class Admin::EmbeddingController < Admin::AdminController

  before_action :fetch_embedding

  def show
    render_serialized(@embedding, EmbeddingSerializer, root: 'embedding', rest_serializer: true)
  end

  def update
    if params[:embedding][:embed_by_username].blank?
      return render_json_error(I18n.t('site_settings.embed_username_required'))
    end

    Embedding.settings.each do |s|
      @embedding.send("#{s}=", params[:embedding][s])
    end

    if @embedding.save
      fetch_embedding
      render_serialized(@embedding, EmbeddingSerializer, root: 'embedding', rest_serializer: true)
    else
      render_json_error(@embedding)
    end
  end

  protected

  def fetch_embedding
    @embedding = Embedding.find
  end
end