Check that the provided token/user has access to write to the space.

In particular, this checks that:

1. The user is either part of the organization to which the space belongs or has the impersonate permission.
2. The space is within the user's space purview.
3. The user has the core_write permission.

Note that some of this is handled by the density_api_view decorator.

If the user has no access, for any reason, this will return a 404. Otherwise, will return a 200 with a JSON body indicating level of access.