(cherry picked from commit bfa534ad)

* Better fix (the page should be there for all flavors)

XWIKI-22649: Error while rendering template [htmlheader.vm] when clicking on 'Forgot your username' and 'Forgot your password' making the templates unreachable

(cherry picked from commit d2d10ed7)

* found some information suggestion that "C.UTF-8" should work fine on Debian 10

(cherry picked from commit 0e07e51d)

* add some explanation on why we use this

(cherry picked from commit b6efa942)

(cherry picked from commit d5d54c22)

(cherry picked from commit 9a6651aa)

XWIKI-22554: Java version verification not performed by XJetty startup script when running in non interactive mode
XWIKI-22555: XJetty startup script returns exit code 0 in case of failure
XWIKI-22556: XJetty systemd service run startup script in interactive mode
(cherry picked from commit 77932127)

(cherry picked from commit c4a0aa0d)

(cherry picked from commit ea4bd72d)

(cherry picked from commit afdfcc25)

(cherry picked from commit 0ddf703f)

(cherry picked from commit 6cf85359)

  * Ignore XWiki.SheetClass which is coming from a legacy module

(cherry picked from commit 2a42110d)

  * Improve test to actually check that XWikiServer page isn't created
    during the build of demo package

(cherry picked from commit 1617473d)

  * Change condition of the test to make it more reliable

(cherry picked from commit 22a10a1b)

  * Provide a test to check that mandatory document initializers are
    properly declared for the demo package
  * Rename and improve the test
  * Put other missing modules

(cherry picked from commit 917d730e)

  * Add missing dependencies to ensure needed xclass are there in the
    demo package

(cherry picked from commit 4ef604e5)

(cherry picked from commit 00096e66)

* fix missing link