The enumerate flag will be read from the cache for subdomains and
the domain object will be created accordingly.

The parameter was not used at all.

When IPA trusts an AD domain the AD user or groups can be placed into
IPA groups e.g. to put AD users under the control of HBAC. Since IPA
group can only have members from the IPA directory tree and the AD users
and groups are not stored there a special IPA object called external
group was introduced. SIDs of users and groups can be added to the
external group and since the external groups are in the IPA directory
tree they can be member of IPA groups.

To speed things up and to remove some load from the IPA servers SSSD
reads all external groups and stores them in memory for some time before
rereading the data.

Enhances https://fedorahosted.org/sssd/ticket/1962

During initgroups request we read the SID of a group from the server but
do not save it to the cache. This patch fixes this and might help to
avoid an additional lookup of the SID later.

In some cases when MPG domains are used the information about the
original primary group of a user cannot be determined by looking at
the explicit group memberships. In those cases the GID related to the
original primary group is stored in a special attribute of the user
object.

This patch adds the GID of the original primary group when available and
needed.

Fixes https://fedorahosted.org/sssd/ticket/2027