Set scim_externalid to nullable, default null

database/migrations/2022_10_25_193823_add_externalid_to_users.php

@@ -14,7 +14,7 @@ class AddExternalidToUsers extends Migration
     public function up()
     {
         Schema::table('users', function (Blueprint $table) {
-            $table->string('scim_externalid');
+            $table->string('scim_externalid')->nullable()->default(null);
         });
     }