WIP Rewite the API provided by all classes under XML/md/

[jaimeperez]

This is quite a big piece of work. Some details:

• [x] Rewrite all classes under XML/md/ to be immutable.
• [x] Redesign the signature-related classes to be interfaces and traits that can be used in whatever element, without messing with the inheritance relationships.
• [x] Add new classes to model missing EndpointType extensions.
• [x] Add new classes to model missing LocalizedNameType extensions.

Some notes on the approach followed:

• Some classes are not abstract, but we want them to be extensible as well. Since we need fromXML() methods for both, the classes extending from the base cannot reuse fromXML() since that one checks the actual element name and namespace URI. An alternative is to create static methods for each property, that return any valid value for it, from a given XML. These methods include all checks needed (e.g. a anyURI type cannot contain an empty string).

• I've used traits to achieve composition of functionality common between different classes. When appropriate, I've added meaningful abstract classes that aggregate functionality coming from those traits (e.g. an AbstractMetadataDocument class that adds properties –and methods– related to any SAML metadata document, like cacheDuration or validUntil).

[tvdijen]

I was able to merge quite a good portion of this PR to master without breaking anything.. That way we at least have some of the individual commits + commit messages instead of one huge squashed commit.

[codecov[bot]]

Codecov Report

Merging #208 into master will increase coverage by 9.58%. The diff coverage is 98.09%.

@@             Coverage Diff              @@
##             master     #208      +/-   ##
============================================
+ Coverage     74.99%   84.57%   +9.58%     
+ Complexity     2294     2122     -172     
============================================
  Files           142      143       +1     
  Lines          5358     5393      +35     
============================================
+ Hits           4018     4561     +543     
+ Misses         1340      832     -508

[tvdijen]

Thanks, I had to run into a meeting :P

[jaimeperez]

No prob! 😄