Convert pretty_reference into a abstract property

This allows us to provide a better references depending on the container type

src/bci_build/package/__init__.py

@@ -982,9 +982,14 @@ def reference(self) -> str:
         pass
 
     @property
+    @abc.abstractmethod
     def pretty_reference(self) -> str:
-        """
-        Returns the human readable pretty URL to this image. Used in image documentation.
+        """Returns the human readable registry URL to this image. It is intended
+        to be used in the image documentation.
+
+        This url needn't point to an exact version-release but can include just
+        the major os version or the latest tag.
+
         """
         return (
             f"{self.registry}/{self._registry_prefix}/{self.name}:{self.version_label}"
@@ -1361,6 +1366,12 @@ def reference(self) -> str:
             + f":{self.version_label}-{self._release_suffix}"
         )
 
+    @property
+    def pretty_reference(self) -> str:
+        return f"{self.registry}/{self._registry_prefix}/{self.name}:" + (
+            "latest" if self.is_latest else self.version_label
+        )
+
     @property
     def build_version(self) -> str | None:
         build_ver = super().build_version
@@ -1441,6 +1452,10 @@ def build_tags(self) -> list[str]:
     def reference(self) -> str:
         return f"{self.registry}/{self._registry_prefix}/bci-{self.name}:{self.version_label}"
 
+    @property
+    def pretty_reference(self) -> str:
+        return f"{self.registry}/{self._registry_prefix}/bci-{self.name}:%OS_VERSION_ID_SP%"
+
 
 def generate_disk_size_constraints(size_gb: int) -> str:
     """Creates the contents of a :file:`_constraints` file for OBS to require