feat: Add shacl checker for modified property of dataset

ogdch.shacl.ttl

@@ -111,7 +111,7 @@
         Refer to the documentation at https://handbook.opendata.swiss/content/glossar/bibliothek/dcat-ap-ch.html#dcat-dataset-publisher
         for Details on this change."""@en ;
   ] ;
-  sh:identifier [
+  sh:property [
       sh:path dct:identifier ;
       sh:minCount 1 ;
       sh:maxCount 1 ;
@@ -120,14 +120,6 @@
         See https://handbook.opendata.swiss/de/content/glossar/bibliothek/dcat-ap-ch.html#dct-identifier-dcat
 	    """@en ;
   ] ;
-  sh:distribution [
-      sh:path dcat:distribution ;
-      sh:minCount 1 ;
-      sh:severity sh:Violation ;
-      sh:message """This dataset does not provide any distributions. Please add at least one distribution for the dataset.
-        See https://handbook.opendata.swiss/de/content/glossar/bibliothek/dcat-ap-ch.html#dcat-distribution-dcat
-	    """@en ;
-  ] ;
   sh:property [
       sh:path dcat:landingPage ;
       sh:nodeKind sh:IRI ;
@@ -158,6 +150,14 @@
         See https://ogdch-new-handbook.clients.liip.ch/de/content/glossar/bibliothek/dcat-ap-ch.html#dct-relation-dcat
         for details."""@en ;
   ] ;
+  sh:property [
+      sh:path dct:modified ;
+      sh:severity sh:Violation ;
+      sh:message """If provided, the modification date should be in ISO-8601 format. See
+         https://ogdch-new-handbook.clients.liip.ch/de/content/glossar/bibliothek/dcat-ap-ch.html#dct-modified-dcat
+         """@en ;
+      sh:datatype xsd:dateTime ;
+  ] ;
   sh:property [
       sh:path dct:accrualPeriodicity ;
       sh:node :FrequencyRestriction ;