Public profile endorsements (accounts picked by profile owner) (#8146)

db/migrate/20180808175627_create_account_pins.rb

@@ -0,0 +1,12 @@
+class CreateAccountPins < ActiveRecord::Migration[5.2]
+  def change
+    create_table :account_pins do |t|
+      t.belongs_to :account, foreign_key: { on_delete: :cascade }
+      t.belongs_to :target_account, foreign_key: { on_delete: :cascade, to_table: :accounts }
+
+      t.timestamps
+    end
+
+    add_index :account_pins, [:account_id, :target_account_id], unique: true
+  end
+end