Enhancement/make unique

[jrausch12]

Many of us in the community use jsonlite to help us get complex structures written to mongo stores. Since there is no support in the mongolite package to set check.names to false when inserting (and also for the sake of best practices) I believe this PR should be merged into a future release.

This will on, duplicate key names, use an underscore notation instead of the default dot notation

[jeroen]

Can you include a minimal example with code that shows the error that you are trying to solve?

[jrausch12]

Can you include a minimal example with code that shows the error that you are trying to solve?

This would be a bit difficult. Essentially, this would enable those writing to mongo databases to respect the reserved dot notation references made when querying a mongo db collection.