Specifically, the CardDAVConnector file can be found at https://github.com/Demelode/thunderbird-ensemble/blob/new_master/modules/connectors/CardDAVConnector.jsm , and its test suite is located at https://github.com/Demelode/thunderbird-ensemble/blob/new_master/tests/test-carddav-connector.js .
Additionally, alongside Alongside other additions such as Memory Cache objects https://github.com/Demelode/thunderbird-ensemble/blob/new_master/modules/connectors/MemoryRecordCache.jsm and the modularization of an open sourced VCard Parser https://github.com/Demelode/thunderbird-ensemble/blob/new_master/modules/lib/VCardParser.jsm , a patch was developed to add promptUsernameAndPassword capabilities to test-prompt-helpers.js in the Mozilla central code base, located at https://bugzilla.mozilla.org/show_bug.cgi?id=906520, as Ensemble will requires its use when requiring CardDAV server authentication.