Backport Identity.uniqueness_scope from EE
Backport Identity.uniqueness_scope from EE

Originates in 'SamlProvider has many linked Identities' from EE

stoplightio/gitlabhq,mmkassem/gitlabhq,jirutka/gitlabhq,dreampet/gitlab,iiet/iiet-git,iiet/iiet-git,stoplightio/gitlabhq,axilleas/gitlabhq,jirutka/gitlabhq,mmkassem/gitlabhq,dreampet/gitlab,iiet/iiet-git,mmkassem/gitlabhq,dreampet/gitlab,dreampet/gitlab,stoplightio/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,jirutka/gitlabhq,jirutka/gitlabhq,axilleas/gitlabhq,axilleas/gitlabhq,axilleas/gitlabhq,iiet/iiet-git