Logging implementation

[gracecodes144]

In order to support PEDSnet auditability, we need to log data views in the app. I propose the following implementation steps:

• Create an avocado_log-like table to log data views. The log record would need to store:
  • The DataContext used. Both the one requested and the one returned after authz modification?
  • The DataView used.
  • The User requesting the view.
  • The time at which the request was made.
  • The result of the request? Was the data delivered?
• Add view log event emitting functionality to the custom QueryProcessor proposed in Add data auth restriction ability #35