refactor: split server modules into smaller more manageable files

modules/nixos-modules/server/home-assistant/database.nix

@@ -0,0 +1,56 @@
+{
+  lib,
+  config,
+  ...
+}: let
+  dbUser = "hass";
+in {
+  config = lib.mkIf config.services.home-assistant.enable (
+    lib.mkMerge [
+      {
+        host = {
+          postgres = {
+            enable = true;
+          };
+        };
+
+        assertions = [
+          {
+            assertion = config.services.home-assistant.database == "postgres";
+            message = "Home Assistant database type must be postgres";
+          }
+        ];
+      }
+      (lib.mkIf config.host.postgres.enable {
+        host = {
+          postgres = {
+            extraUsers = {
+              ${dbUser} = {
+                isClient = true;
+                createUser = true;
+              };
+            };
+            extraDatabases = {
+              ${dbUser} = {
+                name = dbUser;
+              };
+            };
+          };
+        };
+
+        services.home-assistant = {
+          extraPackages = python3Packages:
+            with python3Packages; [
+              psycopg2
+            ];
+        };
+
+        systemd.services.home-assistant = {
+          requires = [
+            config.systemd.services.postgresql.name
+          ];
+        };
+      })
+    ]
+  );
+}