feat: improve UI for timespan inputs on admin page (#726)

* Define Timestamp type

* Implement Timestamp utils

* Implement Timespan input

* Use timestamp input on config page

* Add timespan type to config services

* Refactor maxExpiration to use timespan type across services and components

* Update sessionDuration to use timespan type in config and adjust token expiration logic

* Update localized strings

frontend/src/utils/date.util.ts

@@ -1,4 +1,5 @@
 import moment from "moment";
+import { Timespan } from "../types/timespan.type";
 
 export const getExpirationPreview = (
   messages: {
@@ -30,3 +31,14 @@ export const getExpirationPreview = (
     moment(expirationDate).format("LLL"),
   );
 };
+
+export const timespanToString = (timespan: Timespan) => {
+  return `${timespan.value} ${timespan.unit}`;
+}
+
+export const stringToTimespan = (value: string): Timespan => {
+  return {
+    value: parseInt(value.split(" ")[0]),
+    unit: value.split(" ")[1],
+  } as Timespan;
+};