[#505] create an atomic ACLs endpoint

[d-w-moore]

No test yet, will undraft when I have one.
Exercised now with this script:

# run as rods after 
# $ irm -fr b; itouch b
# $ iadmin mkzone twilight remote
# $ iadmin mkuser dan rodsuser
# $ iadmin mkuser charlie#twilight rodsuser

import irods
from irods.access import iRODSAccess
from irods.exception import iRODSException

s = irods.helpers.make_session()

try:
  pass
  s.acls._call_atomic_acl_api(
   "/tempZone/home/rods/b",
   iRODSAccess("write","","dan"),
   iRODSAccess("write","","public"),
   iRODSAccess("read","","charlie","twilight"),
 )
except iRODSException as exc:
  print(f'{exc!r}')
  e = exc
  print (e.server_msg.get_json_encoded_struct())
#except Exception as exc:
#  print(repr(exc))
else:
  print ('---> success')
  pass