新增：声明感知

db/migrate/20211115014133_create_claims.rb

@@ -0,0 +1,11 @@
+class CreateClaims < ActiveRecord::Migration[5.2]
+  def change
+    create_table :claims do |t|
+      t.integer :issue_id
+      t.integer :user_id
+      t.timestamps
+      t.index :issue_id
+      t.index :user_id
+    end
+  end
+end

db/migrate/20211119135526_add_note_to_claim.rb

@@ -0,0 +1,5 @@
+class AddNoteToClaim < ActiveRecord::Migration[5.2]
+  def change
+    add_column :claims, :note, :text
+  end
+end