feat(grfn/bbbg): Production deployment

Start of a production deployment of the app with nixos+terraform, using
provisioners and null-resources to provision nixos machines a'la espes.

Change-Id: I2ddaed76d0037dadbf9fc9e2ee27e9e67a852228
Reviewed-on: https://cl.tvl.fyi/c/depot/+/4695
Reviewed-by: grfn <grfn@gws.fyi>
Autosubmit: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI

users/grfn/bbbg/shell.nix

@@ -11,6 +11,15 @@ mkShell {
     openjdk11_headless
     postgresql_12
     nix-prefetch-git
+    (writeShellScriptBin "terraform" ''
+      set -e
+      module=$(nix-build ~/code/depot -A users.grfn.bbbg.tf.module)
+      rm -f ~/tfstate/bbbg/*.json
+      cp ''${module}/*.json ~/tfstate/bbbg
+      exec ${depot.users.grfn.bbbg.tf.terraform}/bin/terraform \
+        -chdir=/home/grfn/tfstate/bbbg \
+        "$@"
+    '')
   ];
 
   PGHOST = "localhost";