Add fields related to accessibility regulations to data model

[rhigman]

Related to #577.

New fields required:

• Publisher: "Accessibility contact"
• Publisher: "Accessibility statement" (free text)
• Publication: Accessibility standard(s) compliant with/exempted/not compliant
  • Requires list of standards applicable to each type of publication (e.g. different WCAG standard versions for EPUB vs PDF)

Also update ONIX outputs to include these fields where supported:

• ONIX 3.1 (full "Thoth" output) should support all
• Some platforms may collect some of this information via modified use of pre-3.1 ONIX fields

[ja573]

	WCAG	PDF/UA	EPUB a11y	Exception
Paperback	❌	❌	❌	❌
Hardback	❌	❌	❌	❌
PDF	✅	✅	❌	✅
HTML	✅	❌	❌	✅
XML	✅	❌	❌	✅
Epub	✅	❌	✅	✅
Mobi	✅	❌	❌	✅
AZW3	✅	❌	❌	✅
DOCX	✅	❌	❌	✅
FictionBook	✅	❌	❌	✅
MP3	❌	❌	❌	❌
WAV	❌	❌	❌	❌

✅ = Allowed if it's instead of an exception
❌ = Not allowed

[ja573]

CREATE TYPE accessibility_standard AS ENUM (
    'wcag-21-aa',
    'wcag-21-aaa',
    'wcag-22-aa',
    'wcag-22-aaa',
    'epub-a11y-10-aa',
    'epub-a11y-10-aaa',
    'epub-a11y-11-aa',
    'epub-a11y-11-aaa',
    'pdf-ua-1',
    'pdf-ua-2'
);

CREATE TYPE accessibility_exception AS ENUM (
    'micro-enterprises',
    'disproportionate-burden',
    'fundamental-alteration'
);

ALTER TABLE publication
ADD COLUMN accessibility_standard accessibility_standard, -- WCAG only
ADD COLUMN accessibility_additional_standard accessibility_standard, -- EPUB or PDF only
ADD COLUMN accessibility_exception accessibility_exception,
ADD COLUMN accessibility_report_url TEXT,

-- Either standards or exception (or none, for excluded types)
ADD CONSTRAINT check_standard_or_exception
    CHECK (
        (
            accessibility_exception IS NULL
            AND accessibility_standard IS NOT NULL
        )
        OR (
            accessibility_exception IS NOT NULL
            AND accessibility_standard IS NULL
            AND accessibility_additional_standard IS NULL
        )
        OR (
            accessibility_exception IS NULL
            AND accessibility_standard IS NULL
            AND accessibility_additional_standard IS NULL
        )
    ),

-- Ensure additional_standard is only used for PDFs or EPUBs
ADD CONSTRAINT check_additional_standard_pdf_epub
    CHECK (
        accessibility_additional_standard IS NULL
        OR publication_type IN ('PDF', 'Epub')
    ),

-- Ensure standards are valid per publication type
ADD CONSTRAINT check_accessibility_standard_rules
    CHECK (
        CASE publication_type
            WHEN 'Paperback' THEN accessibility_standard IS NULL AND accessibility_additional_standard IS NULL AND accessibility_exception IS NULL
            WHEN 'Hardback'  THEN accessibility_standard IS NULL AND accessibility_additional_standard IS NULL AND accessibility_exception IS NULL
            WHEN 'MP3'       THEN accessibility_standard IS NULL AND accessibility_additional_standard IS NULL AND accessibility_exception IS NULL
            WHEN 'WAV'       THEN accessibility_standard IS NULL AND accessibility_additional_standard IS NULL AND accessibility_exception IS NULL
            WHEN 'PDF'       THEN (
                (accessibility_standard IS NULL OR accessibility_standard IN (
                   'wcag-21-aa','wcag-21-aaa',
                   'wcag-22-aa','wcag-22-aaa'
                ))
                AND
                (accessibility_additional_standard IS NULL OR accessibility_additional_standard IN ('pdf-ua-1','pdf-ua-2'))
            )
            WHEN 'Epub'      THEN (
                (accessibility_standard IS NULL OR accessibility_standard IN (
                   'wcag-21-aa','wcag-21-aaa',
                   'wcag-22-aa','wcag-22-aaa'
                ))
                AND
                (accessibility_additional_standard IS NULL OR accessibility_additional_standard IN (
                    'epub-a11y-10-aa','epub-a11y-10-aaa',
                    'epub-a11y-11-aa','epub-a11y-11-aaa'
                ))
            )
            ELSE (
                (accessibility_standard IS NULL OR accessibility_standard IN (
                   'wcag-21-aa','wcag-21-aaa',
                   'wcag-22-aa','wcag-22-aaa'
                ))
                AND
                accessibility_additional_standard IS NULL
            )
        END
    );

[rhigman]

Recent guidance on EAA compliance in ONIX from EDItEUR: https://docs.google.com/document/d/1eGF3ieV6nxy--_MZwQ7vWlYUW0GcUBbLE8TXaNWVL-w/