This PR was squashed before being merged into the master branch (closes#6718).
Discussion
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[Validator] Added ISBN validator
Bug fix: no
Feature addition: yes
Backwards compatibility break: no
License of the code: MIT
For information about ISBN-10 and ISBN13: https://en.wikipedia.org/wiki/Isbn
This constraint permits to valid a ISBN-10 code, a ISBN-13 code or both on a value
Commits
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4582261 [Validator] Added ISBN validator
This was implemented in order to satisfy Drupal's requirements for a
singular and a plural message whenever a message is passed to their
implementation of transChoice().
