update_experiment_end_date

Move the end date of ONE running Google Ads or Microsoft Ads experiment, leaving the campaign's other experiments as they are.

                KEYWORDS: experiment, end date, extend, shorten, schedule, stop date, run until

                WHEN TO USE:
                - User wants experiment X to run until a later or earlier date
                - User wants to change one experiment's end date without touching the rest of its campaign

                WHAT THE PLATFORM ALLOWS:
                - Google Ads and Microsoft Ads experiments that are running (Active): this tool.
                - A Completed experiment, any channel: manage_experiment(action="reactivate",
                  end_date=...), which runs it again until that date.
                - A LinkedIn, Facebook, Instagram or Reddit experiment: the platform moves its
                  end date only campaign-wide (add_and_edit_campaign_elements or
                  add_and_edit_native_campaign_elements, which move every experiment of that
                  campaign). This tool refuses them and changes nothing.
                - A Paused experiment: its end date moves only while it runs; restart it
                  (manage_experiment) only if the user wants it running again.
                - Google Ads re-applies the experiment's saved countries and states with the
                  date, so the tool refuses Performance Max, an experiment that excludes
                  locations, and one with no saved countries or states.

                PARAMETERS:
                - experiment_id: experimentId from search_experiments
                - end_date: YYYY-MM-DD, today or later and within a year; the experiment runs
                  through that day

                RESULT:
                status="submitted" means the change was sent: the channel applies it in the
                background, and search_experiments shows the new end date once the channel
                confirms. Say it was requested, not that it changed, until a read shows it.
                status="unchanged" means it already ended on that date and nothing was sent.
                success=false comes with an error that says why nothing was changed.

                WARNING: This changes the live schedule of the experiment on the ad channel.