chore: check version by name

Author: staaldraad

nix/packages/lib.nix

@@ -15,8 +15,13 @@
       extraSubstitutions ? { },
     }:
     let
-      inherit (lib) versions getVersion;
-      pgVersion = versions.major (getVersion postgresPkg);
+      pgVersion =
+        if name == psql_15 then
+          "15"
+        else if name == psql_17 then
+          "17"
+        else
+          "unknown";
 
       paths =
         {