Add `/security` endpoints

[pederhan]

These 2 endpoints are missing client methods:

• /security/vul
• /security/summary

They use the new models introduced in the pydantic-v2 branch. Furthermore, it seems like they may be tied to the new pluggable scanner spec version 1.2 (https://github.com/goharbor/pluggable-scanner-spec). I'm not really sure...