feat: User flags (#3353)

* feat: Add user flags concept, for tracking bits on a user

* feat: Example flag usage for user invite resend abuse

server/migrations/20220409222213-user-flags.js

@@ -0,0 +1,14 @@
+'use strict';
+
+module.exports = {
+  up: async (queryInterface, Sequelize) => {
+    return queryInterface.addColumn("users", "flags", {
+      type: Sequelize.JSONB,
+      allowNull: true,
+    });
+  },
+
+  down: async (queryInterface, Sequelize) => {
+    return queryInterface.removeColumn("users", "flags");
+  }
+};