[DA-1389] accept_none_user_for_workspace (#1598)
[DA-1389] accept_none_user_for_workspace (#1598)

* accept_none_user_for_workspace

* Update rdr_service/dao/workbench_dao.py

Co-Authored-By: Michael Mead <28287f2fb7900dfe3031111988c3fd58f5cdfc03@icloud.com>

* Update rdr_service/dao/workbench_dao.py

Co-Authored-By: Michael Mead <28287f2fb7900dfe3031111988c3fd58f5cdfc03@icloud.com>

Co-authored-by: Michael Mead <28287f2fb7900dfe3031111988c3fd58f5cdfc03@icloud.com>

all-of-us/raw-data-repository,all-of-us/raw-data-repository,all-of-us/raw-data-repository