[Feature] CanDB Logger/Audit Trail

[ByronBecker]

Motivation

For historical, audit, or other purposes - developers may want to enable a CanDB logger/audit trail in order to trace access activity over time.

Requirements

• Define the specific use case and type(s) of data required in a CanDB logger (Interview a few developers/large projects both inside and outside the CanDB alpha)
• Determine the appropriate format and structure for storing log data in stable memory
• Determine the size limit of audit data stored within a canister
• Design the CanDB logger API extension, and determine how it will interact with CanDB
• Implement the logger, providing both unit and integration tests (since the logger will use stable memory)