20220901 InfluxDB - master branch - documentation

Expand InfluxDB 1.8 documentation by incorporating material from:

* [Tutorial: Enabling authentication in InfluxDB](https://gist.github.com/Paraphraser/9f3aa21fddd5d4e8141a7ab03ffb4dd7)
* [Tutorial: Enabling UDP support in InfluxDB](https://gist.github.com/Paraphraser/15483641fc657a147dfae7b03d291bc0)

I thought I had already added this material but a Discord question made
me realise I was mistaken.

General tidy-up because a lot of the example material was either wrong
or out-of-date.

Signed-off-by: Phill Kelley <[email protected]>

Author: Paraphraser