sS tb_addCoOwnerToSnippet(S snippetID, S coOwnerName) {
  long userID = tb_userIDForName(coOwnerName);
  if (userID == 0) fail("TinyBrain user not found: " + coOwnerName);
  ret tb_addCoOwnerToSnippet(snippetID, userID);
}

sS tb_addCoOwnerToSnippet(S snippetID, long coOwnerID) {
  ret loadPage(tb_mainServer() + "/tb-int/add-coowner.php?snippet=" + psI(snippetID) + "&coowner=" + coOwnerID + standardCredentials());
}

Began life as a copy of #1029577