Ruby Psych fails to parse correctly formatted YAML dates

[ronaldtse]

metadata:
  title: 'Resolutions of the CGPM: 1st meeting'
  date: 1889-09-28
  source: BIPM - Pavillon de Breteuil
  url: https://www.bipm.org/en/CGPM/db/1
resolutions:
- dates:
  - 1889-09-28

The 1889-09-28 date instances will fail on YAML.load like this:

Failure/Error: YAML.load_file(Pathname.new(f).expand_path.to_s)

Psych::DisallowedClass:
  Tried to load unspecified class: Date
# (eval):2:in `date'
# ./spec/bipm/data/importer/cgpm_spec.rb:8:in `block (2 levels) in <top (required)>'
# ./spec/bipm/data/importer/cgpm_spec.rb:6:in `map'
# ./spec/bipm/data/importer/cgpm_spec.rb:6:in `block in <top (required)>'
# ./spec/bipm/data/importer/cgpm_spec.rb:3:in `<top (required)>'

The reason is the Psych YAML parser at Ruby has the following bug but it was never fixed, for 6 years!
ruby/psych#262

In that ticket some suggested that only "invalid dates" will raise this issue, but the case is all dates will cause this issue. This is frustrating because the YAML spec does support the "Date" type.

Simply speaking:

irb(main):004:0> YAML.load("1900-01-01")
~/.rbenv/versions/3.1.0/lib/ruby/3.1.0/psych/class_loader.rb:99:in `find': Tried to load unspecified class: Date (Psych::DisallowedClass)

[ronaldtse]

Going to change the data to use quoted strings for dates for now until ruby/psych#262 is fixed.