9 digit millisecond dateformat in sync endpoint is unsupported

[r0ssing]

The sync-endpoint query endpoints do not seem to work correctly?
Specifically the endpoints to return rows updated after a provided date. The endpoints seems to return rows updated before the provided date in some cases?
Endpoints in question
.../query/savepointTimestamp?startTime=
../query/lastUpdateDate?startTime=
It might, or might not, be related to the 9 digit millisecond format?

In several places in the code (in e.g. the suitcase client and sync-endpoint) a date format containing 9 digits for milliseconds is used, e.g.

SimpleDateFormat sf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSSSSSSS");

https://github.com/odk-x/sync-endpoint/blob/master/src/main/java/org/opendatakit/aggregate/odktables/DataManager.java:444

I think maybe it should be updated to only use 3 digits, as 9 is not supported and will result in a parsing error if supplied in the URL param?