The resharding operation must fail if a recipient shard would have missed oplog entries from a donor shard. This can likely build on top of the work being done in SERVER-48523.
Unconditionally check the first entry in the oplog when attempting to resume a change stream
Make find/getMore cmd with $_requestResumeToken on oplog collection to report latest oplog entry ts instead of the latest record id seen while generating the response batch.
SBE should obey ASSERT_MIN_TS_HAS_NOT_FALLEN_OFF_OPLOG flag