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

backend/src/utils/date.util.ts

@@ -10,3 +10,20 @@ export function parseRelativeDateToAbsolute(relativeDate: string) {
     )
     .toDate();
 }
+
+type Timespan = {
+  value: number;
+  unit: "minutes" | "hours" | "days" | "weeks" | "months" | "years";
+};
+
+export function stringToTimespan(value: string): Timespan {
+  const [time, unit] = value.split(" ");
+  return {
+    value: parseInt(time),
+    unit: unit as Timespan["unit"],
+  };
+}
+
+export function timespanToString(timespan: Timespan) {
+  return `${timespan.value} ${timespan.unit}`;
+}