text: 
  exports.up = function(knex) {
      return knex.schema.createTable('customers', tbl => {
        tbl.increments();
        tbl.string('first_name', 128).notNullable();
        tbl.string('last_name', 128).notNullable();
        tbl.string('email', 128).unique().notNullable();
        tbl.string('phone_number', 10).notNullable();
      })
    };
  
    exports.down = function(knex) {
      return knex.schema.dropTableIfExists('customers')
    };