Add "Discard Cleaner" page to dashboard UI

[lucasfcunha]

Hi,

This PR closes this issue #1464

Here is the final version of the page:

This is to help people manage the discarded jobs and take action on specific failed jobs or specific exceptions.

At the moment, no modifications to the database have been made, but I believe it would be interesting in the future to have the error_class and error_message in separate columns in the GoodJob::Job table. This way we could add indexes to make some filters more performant and even add a new select to the discarded table to filter by error_class (just like we have for queue and job).

PS: I opened a discussion question about the i18n case, at this moment I added the keys to the other languages with the same value as the English one, let me know what's the best way to handle this.

Thanks!

[lucasfcunha]

@bensheldon I saw your comment here:

#1537

Do you want me to delete the other language files from this PR or do something else?

Let me know if there is anything that you want me to do here before merging it.

[bensheldon]

@lucasfcunha I can take it from here.

Question: I renamed the tab "Discard Cleaner". Do you think "Exception Cleaner" might be more accurate?

[lucasfcunha]

@bensheldon

I like the "Discard Cleaner" name; it gives exactly the meaning of the page. I imagined that the "Cleaner" name would be changed to something else, and I believe you made a good choice.

Thanks for taking care of the last mile of the PR. I'm looking forward to this getting merged into the main branch. For now, we have been pointing at the fork I made so we can use the page, and it's been way easier to handle/take action with discarded jobs.