This is notably useful to detect credentials errors and return a
LOGIN_FAILED when this happens

CouchDB wasn't handling well too many writes at the same time.
Also, it might be useful to save trips sequentially for the
`cozyMetadata.createdAt` field.

We cannot rely on the same date for trips and manual data because we
might end up in this (unlikely, though) situation:

1. Some manual data is sent to the trace server
2. The konnector is run: it finds trips
3. A new trip is sent on the trace server at the same time
4. A new manual data is sent on the trace server at the same time
5. The konnector finds the new manual data with a more recent date than the last
found trip
6. The konnector save the date of the new manual data
7. The new trip won't be found at the next run

For some queries, the trace server accept a startTime parameter.
On the first run, this parameter is the date of the first trip and on
the next runs, it corresponds to the date of the last saved trip.
Depending on the situation, we want to exclude the first return result
as it will include the trip on this exact date.