validateNameIsNotReserved validation rule unnecessarily requires add-on to have been called from CP

[jcogs-design]

Description of the problem
The process of creating a new field from an add-on is documented, including an example code snippet.
When applying this code-snippet from an add-on that is not called from within CP, the field validation step triggers an EE exception error, this effectively prevents add-ons not called from within CP from validating the field before it is saved.

The validation exception is caused by a call to ee()->cp->invalid_custom_field_names() (which exists within the CP model) which simply returns an array of protected strings; there is no apparent reason why this simple method needs to be tied to the CP model (the code comprises 100% regular php).

How To Reproduce
Implement the example code in an addon called from outside the CP.

Error Messages

InvalidArgumentException Caught
No such property: 'cp' on ExpressionEngine\Legacy\Facade

ee/ExpressionEngine/Legacy/Facade.php:128
Stack Trace: Please include when reporting this error

    #0 ee/ExpressionEngine/Legacy/Facade.php(35): ExpressionEngine\Legacy\Facade->get()
    #1 ee/ExpressionEngine/Model/Content/FieldModel.php(567): ExpressionEngine\Legacy\Facade->__get()
    #2 ee/ExpressionEngine/Service/Validation/Validator.php(246): ExpressionEngine\Model\Content\FieldModel->validateNameIsNotReserved()
    #3 [internal function]: ExpressionEngine\Service\Validation\Validator->ExpressionEngine\Service\Validation\{closure}()
    #4 ee/ExpressionEngine/Service/Validation/Rule/Callback.php(30): call_user_func()
    #5 ee/ExpressionEngine/Service/Validation/Validator.php(188): ExpressionEngine\Service\Validation\Rule\Callback->validate()
    #6 ee/ExpressionEngine/Service/Validation/Validator.php(127): ExpressionEngine\Service\Validation\Validator->_validate()
    #7 ee/ExpressionEngine/Service/Model/Model.php(482): ExpressionEngine\Service\Validation\Validator->validate()
    #8 ee/ExpressionEngine/Model/Content/FieldModel.php(107): ExpressionEngine\Service\Model\Model->validate()
    #9 user/addons/jcogs_heffiq/Service/HeffiqUtilities.php(62): ExpressionEngine\Model\Content\FieldModel->validate()
    #10 user/addons/jcogs_heffiq/Tags/Products.php(66): JCOGSDesign\JCOGSHeffiq\Service\HeffiqUtilities->create_ee_field()
    #11 ee/ExpressionEngine/Service/Addon/Module.php(68): JCOGSDesign\JCOGSHeffiq\Tags\Products->process()
    #12 ee/ExpressionEngine/Service/Addon/Module.php(51): ExpressionEngine\Service\Addon\Module->route()
    #13 ee/ExpressionEngine/Service/Addon/Module.php(118): ExpressionEngine\Service\Addon\Module->routeTag()
    #14 ee/legacy/libraries/Template.php(1835): ExpressionEngine\Service\Addon\Module->__call()
    #15 ee/legacy/libraries/Template.php(1510): EE_Template->process_tags()
    #16 ee/legacy/libraries/Template.php(625): EE_Template->tags()
    #17 ee/legacy/libraries/Template.php(248): EE_Template->parse()
    #18 ee/legacy/libraries/Template.php(178): EE_Template->fetch_and_parse()
    #19 ee/legacy/libraries/Core.php(811): EE_Template->run_template_engine()
    #20 ee/legacy/controllers/ee.php(53): EE_Core->generate_page()
    #21 [internal function]: EE->index()
    #22 ee/ExpressionEngine/Core/Core.php(268): call_user_func_array()
    #23 ee/ExpressionEngine/Core/Core.php(124): ExpressionEngine\Core\Core->runController()
    #24 ee/ExpressionEngine/Boot/boot.php(184): ExpressionEngine\Core\Core->run()
    #25 public_html/index.php(173): require_once('...')
    #25 public_html/index.php(173): require_once('...') 

Environment Details:

• Version: 7.4.9
• PHP Version 8.3

Possible Solution
Relocate the invalid_custom_field_names method to somewhere that accessible all the time... ?