feat: import/export system config

PluralKit.Core/Utils/BulkImporter/PluralKitImport.cs

@@ -30,6 +30,20 @@ public partial class BulkImporter
 
         await _repo.UpdateSystem(_system.Id, patch, _conn);
 
+        var configPatch = new SystemConfigPatch();
+
+        if (importFile.ContainsKey("config"))
+            configPatch = SystemConfigPatch.FromJson(importFile.Value<JObject>("config"));
+
+        if (importFile.ContainsKey("timezone"))
+            configPatch.UiTz = importFile.Value<string>("timezone");
+
+        configPatch.AssertIsValid();
+        if (configPatch.Errors.Count > 0)
+            throw new ImportException($"Field config.{patch.Errors[0].Key} in export file is invalid.");
+
+        await _repo.UpdateSystemConfig(_system.Id, configPatch, _conn);
+
         var members = importFile.Value<JArray>("members");
         var groups = importFile.Value<JArray>("groups");
         var switches = importFile.Value<JArray>("switches");