Automatic retries

[Doerge]

Adds retries on 500, and a few Hackney specific errors.
Retries are not enabled unless the retry_opts option is given to the request:

AWS.Client.request(..., retry_opts: [max_retries: 3, base_sleep_time: 10, cap_sleep_time: 1000])

I don't fully understand the implications of enabling it by default, hence the caution here.

[onno-vos-dev]

Closes #120

[onno-vos-dev]

Thank you @Doerge for picking up this open issue! 🎉 ❤️ I've left two comments, one I believe is a must to maintain backwards compatibility and not retry unless specifically asked for. Unless I'm mistaken 😄

[Doerge]

I was apparently half asleep, because I had forgotten to actually jitter the sleep time.. 😅
I also added an argument to opts to make it a bit more ergonomic:
AWS.Client.request(..., enable_retries?: true) will now enable it with default values. Only if you want to adjust the specific values are retry_opts needed.
I'd recommend a squash-merge, this ended up a bit messy.

[onno-vos-dev]

Will wait a day or two to see if @philss finds anything I missed but otherwise I'll merge this on Friday when I have some time set aside for aws-beam/aws-codegen#109 and I can deal with both at once as well as roll out a new release 🥳🥳🥳

[onno-vos-dev]

Manually squashed everything down (I don't like doing it from the Github UI). Waiting for the build and will merge then 👍

[philss]

Hey, it looks good to me!

I added a few minor suggestions.

If it's too much for this PR, we can tackle that in another one.
And sorry for the delay to review 😬

[philss]

Sweet! 🚢

[onno-vos-dev]

I would say let's merge. WDYT @philss ?

[philss]

@onno-vos-dev yeah, let's merge! 🚀

[onno-vos-dev]

Thank you @Doerge will tag a release shortly