Create a managed space grant

Gives an audience access to a Space or path. Use it to make a Space public, or to share it with the team or one person. The body names the audience: public, team, person, or an external identity that one of the team's identity connections authenticates. The response includes the runtime update when it continues in the background. A grant whose point is commenting (comments.write without content.publish or access.manage) must target where Comments run: a live target needs the Space's comments surface set to everywhere. Otherwise 422 comments_target_unavailable.