feat(declarativeSettings): support sensitive Declarative settings values encryption

[andrey18106]

Related to: nextcloud/server#53121

Implement sensitive Declarative settings encryption for ExApps.

[oleksandr-nc]

In context agent we use appconfig_ex.get_value to read declarative setting values(from fast search by repo sources, @janepie knows for sure).

I guess, that decryption for sensitive values should be added there as well?

[janepie]

In context agent we use appconfig_ex.get_value to read declarative setting values(from fast search by repo sources, @janepie knows for sure).

I guess, that decryption for sensitive values should be added there as well?

Yes, also set_value right now

[kyteinsky]

🚀