feat: "xmp" is no longer a valid package link property

The following entries were removed from the metadata link vocabulary in
EPUB 3.3, due to low usage report:

- the "acquire" relationship
- the "xmp" property

This commit removes the "xmp" from the link property vocabulary, so any
use of it will be reported as an error.

It keeps the "acquire" property in the relationship vocabulary, for
backward compatibility notably with the EPUB Previews specification were
it is defined.

Close #1457

src/main/java/com/adobe/epubcheck/vocab/PackageVocabs.java

@@ -82,7 +82,8 @@ public static enum ITEMREF_PROPERTIES
 
   public static enum LINKREL_PROPERTIES implements PropertyStatus
   {
-    ACQUIRE,
+    ACQUIRE, // note: no longer defined in EPUB 3.3, but still accepted for
+             // backward compatibility with the EPUB Previews specification
     ALTERNATE,
     MARC21XML_RECORD(DEPRECATED),
     MODS_RECORD(DEPRECATED),
@@ -123,7 +124,6 @@ public boolean isDeprecated()
   public static enum LINK_PROPERTIES
   {
     ONIX,
-    XMP;
   }
 
   private PackageVocabs()

src/main/resources/com/adobe/epubcheck/messages/MessageBundle.properties

@@ -190,7 +190,7 @@ OPF_086_SUG.marc21xml-record=the "record" keyword and the media-type "applicatio
 OPF_086_SUG.mods-record=the "record" keyword and the media-type "application/mods+xml"
 OPF_086_SUG.onix-record=the "record" keyword with the properties attribute value "onix"
 OPF_086_SUG.xml-signature=no signature-identifying link
-OPF_086_SUG.xmp-record=the "record" keyword with the properties attribute value "xmp"
+OPF_086_SUG.xmp-record=the "record" keyword
 OPF_086b=epub:type value "%1$s" is deprecated. Consider using %2$s instead.
 OPF_086b_SUG.default=a custom prefixed value
 OPF_086b_SUG.annoref=open annotations

src/test/resources/epub3/03-resources/files/file-url-in-package-document-error.opf

@@ -1,17 +1,18 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<package xmlns="http://www.idpf.org/2007/opf" version="3.0" xml:lang="en" unique-identifier="q">
-<metadata xmlns:dc="http://purl.org/dc/elements/1.1/">
-  <dc:title id="title">Minimal EPUB 3.0</dc:title>
-  <dc:language>en</dc:language>
-  <dc:identifier id="q">NOID</dc:identifier>
-  <meta property="dcterms:modified">2017-06-14T00:00:01Z</meta>
-  <link href="file:example" rel="acquire" media-type="text/html"/>
-</metadata>
-<manifest>
-  <item id="content_001"  href="content_001.xhtml" media-type="application/xhtml+xml"/>
-  <item id="nav"  href="nav.xhtml" media-type="application/xhtml+xml" properties="nav"/>
-</manifest>
-<spine>
-  <itemref idref="content_001" />
-</spine>
-</package>
+<package xmlns="http://www.idpf.org/2007/opf" version="3.0" xml:lang="en" unique-identifier="q"
+  prefix="test: https://example.org">
+  <metadata xmlns:dc="http://purl.org/dc/elements/1.1/">
+    <dc:title id="title">Minimal EPUB 3.0</dc:title>
+    <dc:language>en</dc:language>
+    <dc:identifier id="q">NOID</dc:identifier>
+    <meta property="dcterms:modified">2017-06-14T00:00:01Z</meta>
+    <link href="file:example" rel="test:rel" media-type="text/html"/>
+  </metadata>
+  <manifest>
+    <item id="content_001" href="content_001.xhtml" media-type="application/xhtml+xml"/>
+    <item id="nav" href="nav.xhtml" media-type="application/xhtml+xml" properties="nav"/>
+  </manifest>
+  <spine>
+    <itemref idref="content_001"/>
+  </spine>
+</package>

src/test/resources/epub3/D-vocabularies/files/link-rel-record-properties-valid.opf

@@ -7,7 +7,6 @@
         <dc:identifier id="uid">NOID</dc:identifier>
         <meta property="dcterms:modified">2019-01-01T12:00:00Z</meta>
         <link rel="record" href="onix.xml" media-type="application/xml" properties="onix"/>
-        <link rel="record" href="xmp.xml" media-type="application/xml" properties="xmp"/>
         <link rel="record" href="other.xml" media-type="application/xml" properties="my:type"/>
     </metadata>
     <manifest>

src/test/resources/epub3/D-vocabularies/metadata-link.feature

@@ -15,8 +15,11 @@ Feature: EPUB 3 — Vocabularies — Metadata link vocabulary
 
   #### D.4.1.1 acquire
 
-  @spec @xref:sec-acquire
   Scenario: an 'acquire' link can identify the full version of the publication
+    Note:
+      the 'acquire' relationship was removed in EPUB 3.3:
+      see https://github.com/w3c/epub-specs/issues/2489
+      it is still accepted, for backward compatibility. 
     When checking file 'link-rel-acquire-valid.opf'
     Then no errors or warnings are reported
 
@@ -69,10 +72,6 @@ Feature: EPUB 3 — Vocabularies — Metadata link vocabulary
     Then error OPF-094 is reported
     And no other errors or warnings are reported
 
-  Scenario: a 'record' link type can be further identified with a 'properties' attribute
-    When checking file 'link-rel-record-properties-valid.opf'
-    And no errors or warnings are reported
-
   @spec @xref:sec-record
   Scenario: a 'record' link cannot refine another property or resource
     When checking file 'link-rel-record-refines-error.opf'
@@ -117,3 +116,11 @@ Feature: EPUB 3 — Vocabularies — Metadata link vocabulary
     And error OPF-093 is reported
       # note: 'media-type' is now required, even on deprecated properties
     And no other errors or warnings are reported
+
+
+  ### D.4.2 Link properties
+
+  @spec @xref:sec-link-properties
+  Scenario: a 'record' link type can be further identified with a 'properties' attribute
+    When checking file 'link-rel-record-properties-valid.opf'
+    And no errors or warnings are reported