Forwarded user role assignments `GET` request has `user` filter array collapsed to single value

[Laukei]

Hello! 👋 I've discovered what looks like an issue with forwarding on requests to the facts router, where it collapses the input user filtering to a single value. It may affect other filters - I've only tested user though. The result of this is that a request for users user_1 and user_2 filters to only return user_2.

From the code I can see that when I send a request to the PDP which it hasn't explicitly got a local implementation for, it forwards it on to the cloud with a log it's doing this.

For the functionality I am building, I am requesting the detailed list role assignments with a user filter that contains several IDs. The request to the PDP looks like:

GET https://pdp:7000/v2/facts/proj_id/env_id/role_assignments?page=1&per_page=2&tenant=tenant_id&user=user_1&user=user_2

I then see a log in the PDP output:

Forwarding facts request: GET https://api.permit.io/v2/facts/proj_id/env_id/role_assignments?page=1&per_page=2&tenant=tenant_id&user=user_2

It looks like the PDP forwards to the cloud API with only the last value as the user filter. I believe from some limited testing with FastAPI that this is because unless FastAPI is told to expect an array for a particular value, it only uses the last defined value.

In the immediate term I can modify my request to speak directly to the Permit cloud API, but it would be useful to fix this in the PDP.