init project

db/migrate/20200106022157_create_project_trends.rb

@@ -0,0 +1,12 @@
+class CreateProjectTrends < ActiveRecord::Migration[5.2]
+  def change
+    create_table :project_trends do |t|
+      t.integer :user_id
+      t.integer :project_id
+      t.references :trend, polymorphic: true, index: true
+      t.string :action_type
+      t.timestamps
+    end
+    add_index :project_trends, [:user_id, :project_id]
+  end
+end