This is a pre-patch for introducing a native enum for
DuplicationBehavior. In order to prevent changes to the signature of
`$conflictMode` two times, we omit the typehint `string` in v13 and will
change it in v14 immediately to native enum `DuplicationBehavior`.

Resolves: #102149
Related: #101294
Releases: main
Change-Id: I536151486b21f72bd2bc3959fc74e1124552af50
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/81415


Reviewed-by: Nikita Hovratov <nikita.h@live.de>
Tested-by: Thomas Hohn <tho@gyldendal.dk>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Thomas Hohn <tho@gyldendal.dk>
Tested-by: Nikita Hovratov <nikita.h@live.de>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>