Bugfix/security txt policy

[PouleR]

Changes

Add missing 'security_txt_policy_id' for the DomainRouter model and endpoint

Checks

• [X] The version constant is updated in Client.php
• [X] The changelog is updated (when applicable)

[dvdheiden]

Thank you @PouleR for your first contribution! 🎉

I will take a look at it asap.

[WilliamDEdwards]

Type annotation should be int instead of string.

[WilliamDEdwards]

Version should get point version bump as no breaking changes.

[PouleR]

@WilliamDEdwards Done :)