How to (idiomatically) enable multiple instances for services.prometheus.exporters.systemd (for --user functionality)

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I need to publish --user metrics (the like I can find for the particular user via systemctl --user ...) for multiple users, preferably using the existing nixos module system.

For one user this appears to work well:

  services = {
    prometheus = {
      exporters = {
         systemd = {
          enable = true;
          user = "alpha";
          port = 9558;
        };
      };
    };
  };

but I want to instantiate further ones with other port and user values.

Is there an elegant way to do this, or would I have to resort to manually defining these exporters as separate services?