Create concern collector for User and Institution

app/controllers/concerns/collector_controller.rb

+module CollectorController
+  extend ActiveSupport::Concern
+
+  included do
+    before_action :set_collection, only: :show
+  end
+
+  # GET /v1/users/1/collections
+  def index
+    render json: Collection.where(collector: collector)
+  end
+
+  # GET /v1/user/1/collections/1
+  def show
+    render json: @collection
+  end
+
+
+  protected
+
+  def collector
+    raise NotImplementedError
+    #user, id = request.path.split('/')[2, 3]
+    #collector_model = user.singularize.classify.constantize
+    #@collector = collector_model.find(id)
+  end
+
+  def set_collection
+    @collection ||= Collection.find(params[:id])
+  end
+
+end

app/models/concerns/collector.rb

+module Collector
+  extend ActiveSupport::Concern
+
+  included do
+    has_many :collections, as: :collector, dependent: :destroy
+  end
+
+end