Use t.references to generate foreign key column

Use t.references to generate foreign key column and constraint
on zoom_meetings table.

db/migrate/20190930153535_create_zoom_meetings.rb

@@ -9,15 +9,14 @@ class CreateZoomMeetings < ActiveRecord::Migration[5.2]
 
   def change
     create_table :zoom_meetings do |t|
-      t.integer :project_id, null: false, index: true
-      t.integer :issue_id, null: false, index: true
+      t.references :project, foreign_key: { on_delete: :cascade },
+        null: false
+      t.references :issue, foreign_key: { on_delete: :cascade },
+        null: false
       t.timestamps_with_timezone null: false
       t.integer :issue_status, limit: 2, default: 1, null: false
       t.string :url, limit: 255
 
-      t.foreign_key :projects, on_delete: :cascade
-      t.foreign_key :issues, on_delete: :cascade
-
       t.index [:issue_id, :issue_status], unique: true,
         where: "issue_status = #{ZOOM_MEETING_STATUS_ADDED}"
     end

db/schema.rb

@@ -3898,8 +3898,8 @@ ActiveRecord::Schema.define(version: 2019_10_04_133612) do
   end
 
   create_table "zoom_meetings", force: :cascade do |t|
-    t.integer "project_id", null: false
-    t.integer "issue_id", null: false
+    t.bigint "project_id", null: false
+    t.bigint "issue_id", null: false
     t.datetime_with_timezone "created_at", null: false
     t.datetime_with_timezone "updated_at", null: false
     t.integer "issue_status", limit: 2, default: 1, null: false