Add code for revision cleanup (#6442)

* Add initial code for revision cleanup

* Some improvements - code cleanup

* Cleanup logging

* Add button in admin backend to cleanup revisions of a specific pad

* Disable cleanup by default and show errors in admin area

* Improve cleanup code

* Load revisions for cleanup in parallel

* Consider saved revisions during pad cleanup

src/node/utils/Settings.ts

@@ -380,6 +380,14 @@ exports.sso = {
  */
 exports.showSettingsInAdminPage = true;
 
+/*
+ * Settings for cleanup of pads
+ */
+exports.cleanup = {
+  enabled: false,
+  keepRevisions: 100,
+}
+
 /*
  * By default, when caret is moved out of viewport, it scrolls the minimum
  * height needed to make this line visible.