Authentication, sharing read-only projects

[wetneb]

Is your feature request related to a problem or area of OpenRefine? Please describe.
When hosting OpenRefine online, there is interest in controlling project access, either with authentication or by exposing the project as read only.

Describe the solution you'd like
OpenRefine could come with authentication settings to support that natively. Alternatively, if it is not built in, some hooks could be provided to build this functionality as an extension, for instance.

Additional context
https://stackoverflow.com/questions/53808934/openrefine-read-only-instance
https://groups.google.com/forum/#!topic/openrefine/xCs2yiQ8RhU