[TACO] Add oauth-config placeholder to the connector manifest template

Change-Id: I5d8d490aa9faa78da4c3de8f30b365befb72d0c0
Reviewed-on: https://asterix-gerrit.ics.uci.edu/c/asterixdb-clients/+/21338
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Ian Maxon <imaxon@apache.org>