Predefined readonly Group

[gramian]

Dear Developers,

I would like to propose to add a readonly group as predefined group to the config/server-groups.json (see: package/src/main/config/server-groups.json):

        "readonly": {
          "access": [],
          "resultSetLimit": -1,
          "readTimeout": -1,
          "types": {
            "*": {
              "access": [
                "readRecord"
              ]
            }
          }
        },

This would allow to create "safe" readonly users on-the-fly via the setting server.defaultDatabases.

[lvca]

I like it. @gramian would you like to work on this?

[gramian]

Cool. I will send a PR ASAP.