feat(ops/keycloak): Check in initial Keycloak configuration

This is still missing most of the client configuration etc., in part
due to bugs in the provider which are preventing resource imports.

Change-Id: Ic224ffc001f8e1fe6dcd47b7d002580fdf7b0774
Reviewed-on: https://cl.tvl.fyi/c/depot/+/4628
Tested-by: BuildkiteCI
Autosubmit: tazjin <mail@tazj.in>
Reviewed-by: Profpatsch <mail@profpatsch.de>

ops/keycloak/default.nix

@@ -0,0 +1,8 @@
+{ depot, pkgs, ... }:
+
+depot.nix.readTree.drvTargets {
+  # Provide a Terraform wrapper with the right provider installed.
+  terraform = pkgs.terraform.withPlugins(p: [
+    p.keycloak
+  ]);
+}