[QGIS-Developer] Processing Help system

[matteo]

Hi devs,

I want to share a super brief summary of the brainstorming we had on
this topic. I think it is better to speak about it in Madeira with all
the interested people.

There are some small issues with the Help system and Processing (sphinx
related): that is, URLs build from the Help system are (sometimes)
different from those generated from Sphinx.

Differences are:

* Help system build URL with providerId/groupId/algorithmName.html
* provider "native" is not present in sphinx
* Help system concatenates words (eventually) while sphinx puts `-`
between words

At the end, for some algorithm, we have documentation already merged,
but unreachable from the UI of Processing, e.g.:

1. Help system URL:

https://docs.qgis.org/testing/en/docs/user_manual/processing_algs/native/vectoroverlay.html#lineintersections

2. doc URL:

https://docs.qgis.org/testing/en/docs/user_manual/processing_algs/qgis/vector_overlay_tools.html#line-intersections

I hope interested people can jump in this discussion on share some thoughts!

Cheers

Matteo