add announcements model and migration

server/api/models/announcement.js

@@ -0,0 +1,8 @@
+module.exports = (sequelize, DataTypes) => {
+  const announcement = sequelize.define('announcement', {
+    announce: DataTypes.STRING,
+    until: DataTypes.DATE
+  }, {})
+
+  return announcement
+}

server/migrations/20200215153310-create-announcement.js

@@ -0,0 +1,29 @@
+module.exports = {
+  up: (queryInterface, Sequelize) => {
+    return queryInterface.createTable('announcements', {
+      id: {
+        allowNull: false,
+        autoIncrement: true,
+        primaryKey: true,
+        type: Sequelize.INTEGER
+      },
+      announce: {
+        type: Sequelize.STRING
+      },
+      until: {
+        type: Sequelize.DATE
+      },
+      createdAt: {
+        allowNull: false,
+        type: Sequelize.DATE
+      },
+      updatedAt: {
+        allowNull: false,
+        type: Sequelize.DATE
+      }
+    })
+  },
+  down: (queryInterface, Sequelize) => {
+    return queryInterface.dropTable('announcements')
+  }
+}