TASK: identify .NET Framework dependencies

[johnhenley]

DNN Community Forums obviously has dependency on DNN Platform, and therefore .NET Framework. In addition, module was built for webforms and therefore has dependency on system.web.

As part of our modernization journey, we continue to decouple logic code from UI and webforms, with an ultimate goal of removing webforms altogether in a future release. Not going to happen overnight but we're getting closer with each release. As part of this effort, we need to identify and try to replace system.web API usage with an equivalent API that uses .NET standard 2.0 perhaps or stands alone.