Support GHC-8.4.1 and newer deps

[phadej]

No description provided.

[jkarni]

@phadej maybe cherry-picking from the commits that are going into master would make more sense? Otherwise we have two entirely different sets of commits on this branch and on the release branch, but doing the same things.

[phadej]

I was slightly against doing one-by-one updates in master anyway (especially as it was known that there are other outdated dependencies).

But I'll forward port this to master, when postgresql-client, http-media and servant-auth allows it.

[phadej]

@jkarni I don't see a problem with diverging histories, there is no intention they would converge.

Sorry for not addressing your comment properly. I feel there is a lot of pressure to put stuff out for GHC-8.4.1 or in into master.

As I said previously, I'd rather not merge exceptions #924 (yesterday) neither aeson #919 (5 days ago) PR, but wait till there's time to do this. I also would like to wait till http-media maintainer has time to react in zmthy/http-media#25