Add on_error handler

[towhans]

This allows handling cases when Hammer Backend returns {:error, ...} tuple. For example Hammer.Backend.Redis can return {:error, %Redix.ConnectionError{}} which is not technically an over limit return value but more of a Internal Server Error response.

This will allow to return 500 https status code in case Hammer.Backend returns an {:error, _} which is now impossible because the on_deny handler is called both for :deny and :error The new optional handler can handle error case.

[ruslandoga]

👋 @towhans

Wouldn't it be easier if status=500 is returned by default on all errors?

I'm working on a new API for Hammer ExHammer/hammer#104 and right now I think the backends would only return allow or deny, and all backend errors would be exceptions.

[towhans]

Currently if Hammer.Backend.Redis returns {:error, %Redix.ConnectionError{}} then Hammer itself returns deny. Not an error. It's covering that error up. Raising exceptions would also be a good way to surface the error 👍

[epinault]

if you can rebase I will merge this . Just know this library will then be also EOL anyway soon enough .I am working on the 7x. final release candidate soon and that lib will not longer be useful

[towhans]

Thanks @epinault Rebased.

[epinault]

I created a release just for this on 3.2.0. This package is still EOL as it won t work well with how hammer was rearchitecture and this plug dont provide much benefits long terms.