Method to persist settings

[Startouf]

Suppose I have a Hash setting with nested values. Saving a nested value won't cause settings to be persisted

MySettings.blacklist_by_type # => { abuse: [], hack_attempt: [] }
MySettings.blacklist_by_type[:abuse] = my_blacklist #=> MySettings are not persisted !

I suggest making a persist or save method available as class method MySettings.save