As an ... I want to ... in order to ...

Problem:
in the case of a timeout during saving, i want to be able to try and save again in the hopes that the circumstances have changed.

Example:

• server responds with bad data (e.g. some html)
• server responds with server error (e.g. 500)

Screenshots/mockups:
TODO Charlie

BDD
GIVEN a Bridge edit
WHEN the edit times out
THEN a dedicated error screen is shown
AND the user can dismiss it (return to edit form) or retry (directly resend edit)

Acceptance criteria:

• error message is shown on timeout on save
  • don't purge cache in this case (see T235208)
• user can retry the edit by clicking a retry button
• user can retry the edit by dismissing the error and clicking publish again (different from the cancel button for the error on load!)

Notes:

• user treatment is identical to T245501 but with different error messages