Default expiration date not shown when first creating a share

Steps to reproduce

1. Let the admin configure a "default expiration date for shares" under /settings/admin/sharing, e.g. to 7 days.
2. Open the iOS Files app
3. Click on the share icon next to a file
4. Two options with the same bug:
   a. Either click "Share link"
   b. Or search for a user and select them

Expected behaviour

The "Set expiration date" field should have the date set, e.g. to 7 days in the future.

Actual behaviour

The "Set expiration date" field is empty.

Only after saving the share the expiration date is silently set. This is confusing to the user, because it is not transparent why the share suddenly has an expiraton date.

Screenshots

Logs

n/a

Reasoning or why should it be changed/implemented?

The current, buggy behaviour is confusing. It's also inconsistent with the web client, where this bug has been fixed: https://github.com/nextcloud/server/issues/40612

Environment data

iOS version: e.g. iPadOS 17.2

Nextcloud iOS app version: 4.9.6.1

Server operating system: Ubuntu

Web server: Apache

Database: MariaDB

PHP version: 8.2

Nextcloud version: 28.0.0

Start by tracing the two share-creation flows reached from the iOS Files app: “Share link” and selecting a user. Compare how the configured default expiration is represented with the web client behavior described in server issue 40612; done means the “Set expiration date” field visibly shows the configured future date before saving in both flows.