This adds new dimension table to record credential information. Since a
session can have multiple credentials, the wh_session_accumulating_fact
is is linked to the credential_dimensions via bridge tables,
wh_credential_group and wh_credential_group_membership. When a session
is inserted, the credental group and credential dimensions will be
upserted. If the group changed in any way, a new group is inserted along
with all of the corresponding credentials.
Timothy Messier
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