GUID validation is incorrect

[JakubDolba]

current \SilverStripe\SAML\Helpers\SAMLHelper::validGuid allows:

• only uppercase "guid"
  • should be case insensitive
• allows actually invalid values to be considered as valid
  • standard guid should be hex range [0-9a-f]
  • current implementation check [A-Z0-9] which allows non-guid to pass validation

expected result of validation: only valid guid format is passing

[robbieaverill]

Can you please provide some basic examples of what you're finding correct and incorrect? Are you saying that we should only accept A-F range rather than A-Z?

[JakubDolba]

"textual representation of UUID are represented as 32 hexadecimal (base-16) digits"
source: https://en.wikipedia.org/wiki/Universally_unique_identifier

• sometimes (microsoft) surrounds guid with brackets { }

only [0-9A-F] range should be accepted as for example Z is not valid character of guid

example:
valid: 11111111-1111-1111-ffff-000000000000
invalid: 11111111-zzzz-1111-ffff-000000000000

created pull request #22