Solr8 changes how security.json restricts access to GUI

[Oakley, Craig (NIH/NLM/NCBI) [C]]

In Solr 7, we had clauses in our security.json saying

      {
        "name":"all-admin",
        "collection":null,
        "path":"/*",
        "role":"allgen",
        "index":15},
      {
        "name":"all-core-handlers",
        "path":"/*",
        "role":"allgen",
        "index":16},

We granted the role allgen to all users; but this kept our security folk happy 
in that no one could even get to the top level of the Solr GUI without a 
password.

Now under Solr 8, the GUI does not prompt for a password. It just brings you 
into the GUI (albeit a stripped down version, saying such things as "No cores 
available"). By what means can we require a password to get this far? And by 
what means can we prompt for a password in order to get further?