Introduce explicit audit loggers

[prayerslayer]

Fixes #79

Introduces two new components, a HTTP and a S3 audit logger, which provide a function that, when called, will write the provided clojure map to the destination.

I know we wanted to use timbre and provide a single audit log component, but this structure didn't make sense anymore when I realized we need access tokens for the HTTP component and it's thus dependent on the token-refreshing component. I dropped timbre afterwards because I didn't see the benefit anymore - we don't use the string serialization of it, we write our own appenders...

Could be discussed:

• put important part of log function in a go block so that it's async - the application doesn't care about the result anyways / can't/won't handle errors
• make http audit logger less dependent on oauth component, so that it can be used with unsecured APIs
• make http method to use in http audit logger configurable

[dryewo]

👍

[prayerslayer]

👍

[prayerslayer]

Let's release it tomorrow.

[harti2006]

@prayerslayer @dryewo can you please consider https://github.com/zalando/friboo/pull/81 before releasing? We need this for our application.