Add OCPP 1.6 security 3rd edition schema

[goekay]

related: steve-community/steve#1854

schemas and data types from which we generate the POJOs should be part of this library instead of steve.

resource:

• https://openchargealliance.org/ocpp-info-whitepapers/ocpp-1-6-security-whitepaper-3rd-edition/
• https://openchargealliance.org/my-oca/ocpp/

and more specifically, the original download link for the schema:

• https://openchargealliance.org/wp-content/uploads/2025/05/OCPP-1.6-security-whitepaper-edition-3-2-3.zip
• https://openchargealliance.org/download/ce0c42b61f6b82d64c739c0caa7ad1209e2d4e84acca060122fa113d2261e252