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

server/db/migrations/20180721234154_create_project_membership_table.js

@@ -0,0 +1,22 @@
+module.exports.up = knex =>
+  knex.schema.createTable('project_membership', table => {
+    /* Columns */
+
+    table
+      .bigInteger('id')
+      .primary()
+      .defaultTo(knex.raw('next_id()'));
+
+    table.bigInteger('project_id').notNullable();
+    table.bigInteger('user_id').notNullable();
+
+    table.timestamp('created_at', true);
+    table.timestamp('updated_at', true);
+
+    /* Indexes */
+
+    table.unique(['project_id', 'user_id']);
+    table.index('user_id');
+  });
+
+module.exports.down = knex => knex.schema.dropTable('project_membership');