[stable20] Show the actual error on share requests

[backportbot-nextcloud]

⚠️ This backport had conflicts and is incomplete ⚠️

backport of #25185

[rullzer]

/compile amend /

[faily-bot]

🤖 beep boop beep 🤖

Here are the logs for the failed build:

Status of 1739: failure

acceptance-app-files-sharing

• tests/acceptance/features/app-files-sharing.feature:23

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  Scenario: share a file with another user that needs to accept shares        # /drone/src/tests/acceptance/features/app-files-sharing.feature:23
    Given I act as John                                                       # ActorContext::iActAs()
    And I am logged in as the admin                                           # LoginPageContext::iAmLoggedInAsTheAdmin()
    And I act as Jane                                                         # ActorContext::iActAs()
    And I am logged in                                                        # LoginPageContext::iAmLoggedIn()
    And I visit the settings page                                             # SettingsMenuContext::iVisitTheSettingsPage()
    And I open the "Sharing" section                                          # AppNavigationContext::iOpenTheSection()
    And I disable accepting the shares by default                             # SettingsContext::iDisableAcceptingTheSharesByDefault()
    And I see that shares are not accepted by default                         # SettingsContext::iSeeThatSharesAreNotAcceptedByDefault()
    And I act as John                                                         # ActorContext::iActAs()
    And I rename "welcome.txt" to "farewell.txt"                              # FileListContext::iRenameTo()
    And I see that the file list contains a file named "farewell.txt"         # FileListContext::iSeeThatTheFileListContainsAFileNamed()
    When I share "farewell.txt" with "user0"                                  # FilesAppSharingContext::iShareWith()
    And I see that the file is shared with "user0"                            # FilesAppSharingContext::iSeeThatTheFileIsSharedWith()
    And I act as Jane                                                         # ActorContext::iActAs()
    And I open the Files app                                                  # FilesAppContext::iOpenTheFilesApp()
    And I see that the file list does not contain a file named "farewell.txt" # FileListContext::iSeeThatTheFileListDoesNotContainAFileNamed()
    And I accept the share for "/farewell.txt" in the notifications           # NotificationsContext::iAcceptTheShareForInTheNotifications()
      Notifications button in the header could not be found after 100 seconds (NoSuchElementException)
    And I open the Files app                                                  # FilesAppContext::iOpenTheFilesApp()
    Then I see that the file list contains a file named "farewell.txt"        # FileListContext::iSeeThatTheFileListContainsAFileNamed()
    And I open the details view for "farewell.txt"                            # FileListContext::iOpenTheDetailsViewFor()
    And I see that the details view is open                                   # FilesAppContext::iSeeThatTheDetailsViewIsOpen()
    And I open the "Sharing" tab in the details view                          # FilesAppContext::iOpenTheTabInTheDetailsView()
    And I see that the "Sharing" tab in the details view is eventually loaded # FilesAppContext::iSeeThatTheTabInTheDetailsViewIsEventuallyLoaded()
    And I see that the file is shared with me by "admin"                      # FilesAppSharingContext::iSeeThatTheFileIsSharedWithMeBy()

[juliushaertl]

Failure happens on other prs as well