Implemented username reserve feature

server/database/models/pseudonyms.js

@@ -0,0 +1,28 @@
+const Sequelize = require('sequelize');
+const sequelize = require('..');
+
+module.exports = sequelize.define('pseudonyms', {
+	id: {
+		type: Sequelize.INTEGER(11),
+		allowNull: false,
+		autoIncrement: true,
+		primaryKey: true,
+		unique: true
+	},
+
+	username: {
+		type: 'varchar(320)',
+		unique: true
+	},
+
+	pseudonym: {
+		type: 'varchar(320)',
+		unique: true
+	},
+
+	deletion: {
+		type: 'DATETIME',
+		allowNull: true,
+		defaultValue: null
+	}
+});