Add full ISO8601 duration decimal support

In previous commits I added millisecond support for the validUntil
duration field.

It turns out that the ISO8601 spec[1] also supports milliseconds for
some other duration components (S4.4.3.2):

  > If necessary for a particular application, the lowest order
  > components may have a decimal fraction.

Which components this affects is slightly ambiguous; I've interpreted it
to mean the hours, minutes and seconds components.

In part that's because our current implementation uses
DateTime#next_year, #next_month and #next_day to apply all other fields
to the computed duration, and these methods only respect integer step
inputs. They accept floats, but fractional parts are ignored.

This commit therefore adds fractional support to the H/M/S components,
and updates the computation to support a comma decimal separator.

[1] https://www.loc.gov/standards/datetime/iso-tc154-wg5_n0038_iso_wd_8601-1_2016-02-16.pdf

Author: Simon Coffey

lib/onelogin/ruby-saml/utils.rb

@@ -16,18 +16,18 @@ class Utils
       DSIG      = "http://www.w3.org/2000/09/xmldsig#"
       XENC      = "http://www.w3.org/2001/04/xmlenc#"
       DURATION_FORMAT = %r(^
-        (-?)P                         # 1: Duration sign
+        (-?)P                       # 1: Duration sign
         (?:
-          (?:(\d+)Y)?                 # 2: Years
-          (?:(\d+)M)?                 # 3: Months
-          (?:(\d+)D)?                 # 4: Days
+          (?:(\d+)Y)?               # 2: Years
+          (?:(\d+)M)?               # 3: Months
+          (?:(\d+)D)?               # 4: Days
           (?:T
-            (?:(\d+)H)?               # 5: Hours
-            (?:(\d+)M)?               # 6: Minutes
-            (?:(\d+(?:\.\d{3})?)S)?   # 7: Seconds and optional milliseconds
+            (?:(\d+(?:[.,]\d+)?)H)? # 5: Hours
+            (?:(\d+(?:[.,]\d+)?)M)? # 6: Minutes
+            (?:(\d+(?:[.,]\d+)?)S)? # 7: Seconds
           )?
           |
-          (\d+)W                      # 8: Weeks
+          (\d+)W                    # 8: Weeks
         )
       $)x
 
@@ -59,13 +59,8 @@ def self.parse_duration(duration, timestamp=Time.now.utc)
           raise Exception.new("Invalid ISO 8601 duration")
         end
 
-        durYears = matches[2].to_i
-        durMonths = matches[3].to_i
-        durDays = matches[4].to_i
-        durHours = matches[5].to_i
-        durMinutes = matches[6].to_i
-        durSeconds = matches[7].to_f
-        durWeeks = matches[8].to_i
+        durYears, durMonths, durDays, durHours, durMinutes, durSeconds, durWeeks =
+          matches[2..8].map { |match| match ? match.tr(',', '.').to_f : 0.0 }
 
         if matches[1] == "-"
           durYears = -durYears