新增：数据集新字段license_id和paper_content

app/models/project_dataset.rb

@@ -2,21 +2,25 @@
 #
 # Table name: project_datasets
 #
-#  id          :integer          not null, primary key
-#  title       :string(255)
-#  description :text(65535)
-#  project_id  :integer
-#  created_at  :datetime         not null
-#  updated_at  :datetime         not null
+#  id            :integer          not null, primary key
+#  title         :string(255)
+#  description   :text(65535)
+#  project_id    :integer
+#  created_at    :datetime         not null
+#  updated_at    :datetime         not null
+#  license_id    :integer
+#  paper_content :text(65535)
 #
 # Indexes
 #
+#  index_project_datasets_on_license_id  (license_id)
 #  index_project_datasets_on_project_id  (project_id)
 #
 
 class ProjectDataset < ApplicationRecord
 
   belongs_to :project
+  belongs_to :license, optional: true
   has_many :attachments, as: :container, dependent: :destroy
 
 end