get_primary_service doesn't check blocklist or allowed services

[jdm]

The spec annotation steps in #14407 helped me realize that get_primary_service and get_primary_services implement the same algorithm but have different behaviour. The spec says that the service returned from get_primary_service should not be blocklisted and should be in the list of allowed services.

cc @dati91 @zakorgy

[jdm]

get_included_service seems to also be missing these checks.

[dati91]

We check for blocklist here and for the allowed services here.

[jdm]

What is the purpose of checking the blocklist in get_primary_services, in that case?

[jdm]

Disregard that question, I read the code and it makes more sense.