- Improve the Syntax Guide page related to images to use the same terminology

* Better wording for link documentation

* Typo in documentation from previous commit

* Improve the Syntax Guide page related to link (done collaboratively with Eduard Moraru)

XWIKI-13060: Ability to reference Nested Pages as siblings in wiki links when they have the same parent
- Updated the XWiki link syntax documentation page
- Changed wording from "document" to "page"

XWIKI-13060: Ability to reference Nested Pages as siblings in wiki links when they have the same parent

- Updated the link syntax documentation

* fix test

 * Fixed remaining regression

[Misc] Add new API to be able to get the content of errors (related to https://github.com/xwiki-contrib/application-antispam/commit/1430afc432730fc3e052502cc8d33deb457fe3e4)

- Fixed NPE cause by the ExecutionContext/XWikiContext not being initialized by the time ConversionFilter is executed
-- Fixed by adding a null check in DAB.exists(documentReference) but other methods will fail if called in this timeslot.
-- Also using the XWikiContextProvider in DAB, but this does not help much, since that does nothing if ExecutionContext is not yet initialized, and it is not.
- Fixed test

* Fix test accordingly + moved test from enterprise to platform

* update test

* add tests

* optimizations (thanks to Enygma2002)

* fix tests

* fix bug

* don't fallback if target document is current document

* Fix potential NPE that the previous commit will cause when no "language" parameter is passed

- Added an example on the image syntax with the no-WebHome syntax

- Added more examples in the link syntax documentation

- Updated the syntax documentation to mention:
-- the new space: type and
-- the untyped link resolution algorithm
- Added some extra Nested Pages details (e.g. spaceNameList)

* Fix the regression caused by previous commits in the MailSender module

- Fixed leftover bad assumption

- Removed another leftover

- Fixed bad assumption on the result of the resolvers.

- Removing leftovers that were causing unresolved dependency issues