Bug 21998: Add pattern parameter in Koha::Token

Bug 21998: Add pattern parameter in Koha::Token

Allow a pattern too in Koha::Token->generate. Only supported length.
Does not affect CSRF calls. So tiny change without further impact.

Test plan:
Run  t/Token.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit b794643bb075c0aa5de81f2481ae1df56f674309)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>