[READY] v2.x - Rework SP request UUID generation to remove mutable constant

[johnnyshields]

This PR reworks the way SP request UUID generation is handled.

• Replace the mutable RubySaml::Utils::UUID_PREFIX constant and set_prefix method with Settings.sp_uuid_prefix
  • (Mutable constants are not thread-safe, violate principle of least surprise, etc.)
• Make Authnrequest, etc. uuid attribute to be immutable.
• Initialize Authnrequest, etc. uuid attribute when create is called, based on Settings.sp_uuid_prefix, not when instantiating the Ruby object.

[johnnyshields]

@pitbulk would like to get your feedback on this. I am OK to keep the Authnrequest.uuid = mutator method if there's really a use case for it.

Edit: I've decided to leave the mutator in, so as to minimize change and provide users a workaround if they need it.

[pitbulk]

@johnnyshields it seems tests are failing.

[johnnyshields]

@pitbulk This is ready for final review.

[johnnyshields]

1 failure due to that JRuby Zlib issue still. Seems my previous fix didn't resolve it... This is fine to merge.

[pitbulk]

@johnnyshields, now that prefix can be defined, I believe that should be mentioned what the spec requires in terms of the possible values to be set for the ID attribute:

The type xsd:ID is used for an attribute that uniquely identifies an element in an XML document. An xsd:ID value must be an NCName. This means that it must start with a letter or underscore, and can only contain letters, digits, underscores, hyphens, and periods.

[johnnyshields]

@pitbulk please check now.