Case-insensitive Nice URLs

## Gentics Mesh Version, operating system, or hardware.
- v1.6+

## Operating System
- Any

## JVM
- Any

## Problem
Currently so called "Nice URLs" are case-sensitive, i.e. tell apart **/nice_url** and **nice_URL**. Although [W3C standard](https://www.w3.org/TR/WD-html40-970708/htmlweb.html) states URLs being case-sensitive by default, it also allows URL parts not following the case sensitivity. Implementing the optional case insensitivity for Nice URLs may be a useful feature.

The issue does not name implementation files, entry points, or tests. Trace the existing Nice URL handling and its tests first, then determine how optional case-insensitive matching should be configured and verified. Done means Nice URLs can match differing letter cases when enabled without changing default behavior.

Written by the indexing model from the issue text.