Why does my content object not show up in the portal_catalog?

I am trying to implement a basic Zope2 content type directly without using dexterity or Archetypes because I need this to be extremely lean.

from OFS.SimpleItem import SimpleItem
from Products.ZCatalog.CatalogPathAwareness import CatalogAware
from persistent.list import PersistentList

class Doculite(SimpleItem, CatalogAware):
    """ implement our class """

    meta_type = 'Doculite'

    def __init__(self, id, title="No title", desc=''):
        self.id = id
        self.title = title
        self.desc = desc
        self.tags = PersistentList()
        self.default_catalog = 'portal_catalog'

    def add_tags(self, tags):
        self.tags.extend(tags)

    def Subject(self):
        return self.tags

    def indexObject(self):
        self.reindex_object()

From an external method I am doing this:

def doit(self):
    pc = self.portal_catalog
    res1 = pc.searchResults()
    o1 = self['doc1']
    o1.add_tags(['test1', 'test2'])
    o1.reindex_object()
    res2 = pc.searchResults()
    return 'Done'

I clear the catalog and run my external method. My object does not get into the catalog. But from the indexes tab, when I browse the Subject index, I can see my content item listed with the values. Both res1 and res2 and empty.

Why is my content item not showing up inside the searchResuts() of the catalog?

Plone needs every content object to provide an "allowedRolesAndUsers" index to return the object in searchResults.

There is probably a zcml snippet that will enable this for my content type. But I was able to get things working by adding another method as follows:

def allowedRolesAndUsers(self):
    return ['Manager', 'Authenticated', 'Anonymous']