fix: allow deleting non existing flag

[Gladear]

Attempt to fix #26

It's pretty hard to test if it actually works since I don't have multiple nodes to test, so sorry if the fix isn't correct 😕

[tompave]

Hi @Gladear , thank you for iterating on this. I'd ask to please not commit --amend and force push. It blows away the PR history, and it makes it difficult to see what changed. You can simply add a new incremental commit and push.

[tompave]

Ok, I think this works in theory, thank you.

However, I don't think that the error from https://github.com/tompave/fun_with_flags_ui/issues/26 comes only from the delete "/flags/:name/boolean" endpoint you've modified. As I mentioned here, the problem is more widespread. I think that all endpoints need to switch to logic that ensures that String.to_existing_atom/1 doens't just rely on what's available in memory.

From the original message:

It's pretty hard to test if it actually works since I don't have multiple nodes to test, so sorry if the fix isn't correct

On the master branch of FWF I've added some instructions on how to run multiple nodes: https://github.com/tompave/fun_with_flags#working-with-pubsub-locally

But I don't think you need that. You can restart the FWF.UI app (iex -S mix) and go directly to a flag details page without first loading the homepage.