Let a guest actually use search: declare the shipped guest grants, and draw the box for whoever can search

plugins/guides/plugin.py

@@ -74,6 +74,25 @@ class GuidesPlugin(BasePlugin):
             ('guides.delete', 'Delete guides', 'guides'),
         ]
 
+    def get_guest_grantable_permissions(self) -> List[str]:
+        """A procedure is for whoever is standing at the machine.
+
+        Guides are written to be followed on the floor, by people who often
+        have no account and no reason to get one. The nav item and the API
+        route both already reason about a signed-out reader holding this, so
+        the grant was intended from the start; it qualified under the old
+        .view suffix rule and is written down here now that a grant has to be
+        declared.
+
+        What it reaches is bounded by the routes, not by this: list_guides
+        returns published guides only, matching search against the PUBLISHED
+        revision so draft wording cannot leak through a hit, and a guest can
+        never take the author branches because a guest has no user id. Guide
+        history stays with the editors. Publishing, editing and deleting are
+        separate permissions and none of them is grantable.
+        """
+        return ['guides.view']
+
     def get_navigation_items(self) -> List[Dict]:
         # Position 8, directly under Slides (7), rather than down in the
         # Information section with the reference lists. A guide is something you