Add expires_at field to personal_access_tokens table

Author: relliv

database/migrations/2019_12_14_000001_create_personal_access_tokens_table.php

@@ -20,6 +20,7 @@ public function up()
             $table->string('name');
             $table->string('token', 64)->unique();
             $table->text('abilities')->nullable();
+            $table->timestamp('expires_at')->nullable();
             $table->timestamp('last_used_at')->nullable();
 
             $table->timestamps();