Import/Export to file

[markphelps]

What

I'd like to be able to export all flags, variants, segments, constraints and rules to a file (YAML/TOML/your favorite ML).

This would allow storing all configuration in source control as well as provide a simple way to backup data.

I'd also like to be able to import previously exported data

I'm thinking this would require two new commands flipt import and flipt export with options for the file name and type (yaml/toml/json/etc).

Open Questions:

1. What to do when there is conflicting data/data already exists during import?

It could make sense to add an option to drop all existing data before importing by providing a -drop or -delete option such as https://github.com/Unleash/unleash/blob/master/docs/import-export.md

[markphelps]

Tracking in https://github.com/markphelps/flipt/compare/import-export