Old user/developer upgrade guide page should be removed
The user and developer upgrade guides have migrated to the wiki, but pages for older releases and https://www.openfoam.com/documentation still point to the old guides, which give a miserable impression of not being updated. The old web-pages should probably be removed and the release pages, as well as https://www.openfoam.com/documentation should link to the Gitlab wiki.
I think the spread of parts of documentation across the Gitlab wiki, doxygen (the extended guide), ordinary web-pages, and wiki.openfoam.com is a concern. The above is an example of associated artefacts. Is there some vision for consolidation? In Python, the Sphinx package is commonly used to parse the code like doxygen and then build additional documentation using markdown/rst. There is a C++ parser in Sphinx working on top of doxygen output. Perhaps this approach could be considered?
## Reattaching the author to the issue ticket: @timofeymukha ##