If annotator-store is down, annotator warns users but they may lose work if not careful

[techgique]

This appears to be the case from @ejrau's account of today's downtime. I'll test it when I update servers at night to confirm and investigate a quick fix.

[techgique]

I saw warnings when trying to save, update, or delete annotations while annotator store was down.

Is this enough warning? If one sees these warnings, they may want to copy their annotations into a text file for saving later. Otherwise, one will need to keep the web page open with the changes until annotator-store is back up.

I guess I didn't test if things will be okay when annotator store is down, a user submits a new annotation receiving the warning, annotator-store is brought back up, and then the user tries to save again. The client-side code seems to try to perform an update (a PUT request instead of a POST), but the annotation was never created on the server. Not sure how it handles this.