Protected namespace in localstorage

Is your feature request related to a problem? Please describe.
Starting from version 16, Nextcloud deletes the complete local/sessionstorage. This can cause issues with different apps like ojsxc. I understand the intend to protect users privacy, but it would be nice if this could be configured by the app developer.

https://github.com/nextcloud/server/blob/6f941a73a21ba926cca5b12ecab8242e34169d91/core/src/login.js#L32-L33

Describe the solution you'd like
Black or white list of prefixes which should be deleted or preserved. For example:

   let prefixRegex = new RegExp('^' + prefix);
   let keys = Object.keys(localStorage);

   for (let key of keys) {
      if (prefixRegex.test(key)) {
         localStorage.removeItem(key);
      }
   }

Start at core/src/login.js around lines 32-33, where Nextcloud clears localStorage and sessionStorage. Review how storage keys are removed and how an app-developer-configurable allowlist or blocklist would fit the existing login flow. Done means the requested prefixes are handled without breaking the privacy cleanup, with behavior covered by the relevant tests if available.