core/src/main/java/org/sakaiproject/nakamura/api/lite/authorizable/Authorizable.java
public void addPrincipal(String principal) {
        if (!readOnly && !principals.contains(principal)) {
            principals.add(principal);
            principalsModified = true;
        }
    }
public void addPrincipal(String principal) {
        if (!readOnly && !principals.contains(principal)) {
            principals.add(principal);
            principalsModified = true;
        }
    }
add a principal to this authorizable.
@param principal