Peppol Test Network support for playgrounds

Allow playground teams to connect to the Peppol Test Network for end‑to‑end testing with real Peppol participants.

We’ve added optional Peppol Test Network support for playground environments.

Test Network playgrounds: When creating a playground, you can now choose to connect it to the Peppol Test Network, instead of keeping it fully isolated.
Correct routing and credentials: Documents sent from a Test Network playground use dedicated AP/SMP endpoints and tokens, and companies/identifiers are registered against the matching test infrastructure.
Safer separation from production: Production teams and non‑Test Network playgrounds remain unchanged and do not interact with the Peppol Test Network.

This makes it possible to run realistic end‑to‑end Peppol tests while still keeping production traffic fully separated.