fix: reject unknown epub: attributes in SVG

The spec only requires SVG to be well-formed, but one can argue that
attributes in the EPUB namespace can only be defined by the EPUB specs
and therefore should still be validated.

For instance, EPUB already specifies where `epub:type` is allowed in SVG,
as a normative statement.

This commit updates the persmissive SVG schema to reject all attributes
in the `http://www.idpf.org/2007/ops` namespace except the known ones.

Author: rdeltour

src/main/resources/com/adobe/epubcheck/schema/30/mod/epub-svg-forgiving-inc.rnc

@@ -19,7 +19,9 @@
   svg =
     element svg { svg.inner & svg.attrs }
   svg.attrs =
-    ( svg.epubtype.allowed.attrs )
+    ( svg.epubtype.allowed.attrs
+      & epub.prefix.attr.ns?
+    )
   svg.inner =
     ( svg.any.inner )
 
@@ -35,7 +37,7 @@
   svg.generic.attr =
     attribute *
       - ( id
-        | epub:type
+        | epub:*
         ) { text }
 
   # Attribute list of elements where `epub:type` is allowed

src/test/resources/epub3/06-content-document/content-document-svg.feature

@@ -51,6 +51,13 @@ Feature: EPUB 3 — Content Documents — SVG
     And the message contains '"epub:type" not allowed'
     And no other errors or warnings are reported
 
+  Scenario: Report an unknown `epub:*` attribute used in SVG
+    Given the reporting level is set to usage
+    When checking document 'unknown-epub-attribute-error.svg'
+    Then error RSC-005 is reported
+    And the message contains '"epub:unknown" not allowed'
+    And no other errors or warnings are reported
+
 
   ### 6.2.2 SVG requirements