Change id generation algorithm, display notifications total on the main page

server/db/migrations/20181024220134_create_action_table.js

@@ -0,0 +1,24 @@
+module.exports.up = knex =>
+  knex.schema.createTable('action', table => {
+    /* Columns */
+
+    table
+      .bigInteger('id')
+      .primary()
+      .defaultTo(knex.raw('next_id()'));
+
+    table.bigInteger('card_id').notNullable();
+    table.bigInteger('user_id').notNullable();
+
+    table.text('type').notNullable();
+    table.jsonb('data').notNullable();
+
+    table.timestamp('created_at', true);
+    table.timestamp('updated_at', true);
+
+    /* Indexes */
+
+    table.index('card_id');
+  });
+
+module.exports.down = knex => knex.schema.dropTable('action');