Allow wrapping of lockable Warden after sign-in hook

[geoffharcourt]

For applications using a primary/replica multiple database setup, Rails
6's default connection switching can lead to the Lockable after
sign-in hook firing on GET requests, getting the read-only database,
and then attempting to write while zeroing out the user's failed attempts.

This change adds a customizable wrapper proc that can allow applications
to customize this behavior. For a primary/replica setup using
ActiveRecord's default connection switching, it might look like this:

Devise.setup do |config|
  # default is Proc.new { |hook| hook.call }
  config.warden_hook_save_wrapper = Proc.new do |hook|
    # ensure the writable connection is used to avoid read-only write errors
    ApplicationRecord.connected_to(role: :writing) do
      hook.call
    end
  end
end

This ensures that writes don't happen in a read-only connection if that's the
current connection context.

Fix #5264

[geoffharcourt]

Note: I'm not sure how to set up proper Warden hook tests here.

[mhenrixon]

Any news on this? Has been a minute now :)

[carlosantoniodasilva]

Geoff and I have chatted (yesterday actually) about it, and here's the outcome we're going to try: instead of a new configuration to wrap this particular warden hook, we'll expose a model method that will be called from the hook here, similar to how we do for trackable, which will give you control over that in your model code to wrap it and call super.

This way you can at least override all the pieces inside the app to switch to a writing connection in Devise methods. As a second step we can look into making Devise more aware of multi-DB support and have it do the work of switching connections, but that's a bigger change we need to look at more carefully and from a broader perspective.

[carlosantoniodasilva]

@geoffharcourt @mhenrixon I'm giving this one a shot in #5369, let me know about any feedback/concerns there please. Thanks!

[geoffharcourt]

Closing in favor of #5369! Thank you @carlosantoniodasilva!