Administration: Users: Multisite: Allow users to select more than one site

[fitzgerald]

We have some users who need the ability to edit content and productions on more than one site. Currently, users can either be an admin on one site or all sites. Ideally, they would be able to edit one or more sites, not just one or all.

Describe the solution you'd like
Ideally, in the admin-->user-->sites dropdown, they could multiselect multiple sites. This would give access to one or more sites. The user would see those sites in the selection dropdown when they login.

Describe alternatives you've considered
Currently, the only workaround is to give those users access to "Any" and they get all sites.

Additional context