Use Sync adapter to keep memory in sync with storage adapter

initializer.rb

# config/initializers/flipper.rb

require 'flipper/adapters/sync'

Rails.application.configure do
  # Disable per-request memoization
  config.flipper.memoize = false
end

Flipper.configure do |config|
  config.adapter do
    # Primary storage adapter
    storage_adapter = Flipper::Adapters::ActiveRecord.new

    # Memory adapter for fast reads
    memory_adapter = Flipper::Adapters::Memory.new

    # Keep in sync in main thread on an interval
    Flipper::Adapters::Sync.new(memory_adapter, storage_adapter, interval: 10)
  end
end

@bkeepers Does this require a specific branch, or can this be done with main?

@jhubert This works on main