This ticket covers implementing parsing of extended json (canonical and relaxed) into the canonical/relaxed types.

Parse basic types
Parse $regex https://jira.mongodb.org/browse/RUBY-2081
Parse all legal $binary inputs https://jira.mongodb.org/browse/RUBY-2056
Parse legacy $binary representation https://jira.mongodb.org/browse/RUBY-2073
Parse $dbPointer https://jira.mongodb.org/browse/RUBY-2086
Parse $ref https://jira.mongodb.org/browse/RUBY-2087
Review types of raised exceptions https://jira.mongodb.org/browse/RUBY-2088

Follow-up work for this ticket is to consider:

Whether $numberDecimal inputs should be returned as Ruby BigDecimal instances in relaxed mode
Whether regular expression inputs should be returned as Ruby regular expressions (all or potentially only those with m flag set)