* new slog in stdlib is utilized for that and replaces 'log' pkg
* configuration pkg is used validate and now set/define/refer
  log level values
* the 'error' level call is not fatal, thus os.Exit is called
  instead

See https://github.com/prometheus/docs/blob/496a6ee5ffea8a08f42f98cc7208256d300be015/content/docs/instrumenting/exposition_formats.md

* remove some spaces
* return item.Name() instead of map key
* re-order router log output

Somebody havent heard about SemVer yet. The Ctx.GetReqHeaders() return value
slightly changed (string to []string), which now requires to first join the slice
before checking whether it contains the given string

Initially, that was done to prevent flaky test runs, which turned out
to be caused by Fiber's behaviour (se previous commit).

Using the Param "name" to create an Item and persist turns out to be
affected bi Fiber's behaviour of "zero allocation", which means values
may be re-used across requests/contexts.

This caused wrong or chunked up Item names in the ephemeral state, which
only surfaced during unit testing.

For more details see https://docs.gofiber.io/#zero-allocation

This is to improve/funnel potentially fatal errors

* rework indentation of some configuration variables
* rename some 'err' variables to '_' since they are not used

Available levels for now: debug, error. While the former is the
most verbose one and the latter the least verbose.

It sets it to 'debug' if in development mode.

The version is displayed on the HTML-based landing page.

This is being handled by Fiber, hence not tested.

For now it's just ephemeral.

Instead of disabling the timeout (-1), it's set to 1 ms for all requests
in the state paths test. Otherwise race condistion may occur. Symptoms include
incorrect state name, because it may have been read before it's fully written
to the store.

Depending on whats in the accept request header, the root
path either response with a plain text or some nice HTML.

it appears that order matters; using ctx.JSON overrides c.Type; but
instead of shuffling the lines around, the JSON string is generated
by *foot*, which allows to keep header setting at the beginning of
the function.

* add dependency to allow limiting possible values, though actual
  validation doesnt happen yet
* make variable that indicates health local instead of global

The three dots ('./...') are required to ensure recursive dependency
installation, meaning dependencies of sub-packages.

The three dots ('./...') are required to ensure recursive dependency
installation, meaning dependencies of sub-packages.