Revert SiteMiddleware to setting request.site
Revert SiteMiddleware to setting request.site

This way, SiteMiddleware continues to support existing user / third-party code that has not yet been migrated from request.site to Site.find_for_request

wagtail/wagtail,wagtail/wagtail,timorieber/wagtail,wagtail/wagtail,jnns/wagtail,kaedroho/wagtail,gasman/wagtail,kaedroho/wagtail,takeflight/wagtail,mixxorz/wagtail,kaedroho/wagtail,kaedroho/wagtail,thenewguy/wagtail,takeflight/wagtail,mixxorz/wagtail,rsalmaso/wagtail,wagtail/wagtail,FlipperPA/wagtail,gasman/wagtail,takeflight/wagtail,takeflight/wagtail,rsalmaso/wagtail,thenewguy/wagtail,mixxorz/wagtail,FlipperPA/wagtail,torchbox/wagtail,thenewguy/wagtail,jnns/wagtail,gasman/wagtail,zerolab/wagtail,jnns/wagtail,gasman/wagtail,FlipperPA/wagtail,zerolab/wagtail,FlipperPA/wagtail,torchbox/wagtail,wagtail/wagtail,mixxorz/wagtail,kaedroho/wagtail,zerolab/wagtail,rsalmaso/wagtail,zerolab/wagtail,timorieber/wagtail,timorieber/wagtail,thenewguy/wagtail,mixxorz/wagtail,torchbox/wagtail,torchbox/wagtail,thenewguy/wagtail,zerolab/wagtail,timorieber/wagtail,gasman/wagtail,rsalmaso/wagtail,jnns/wagtail,rsalmaso/wagtail