Add 'get_selectable_groups' method

An earlier oversight - the courts we want to show grouped in the context of the search form are the _selectable_ courts, not the _listable_ ones.

src/ds_caselaw_utils/courts.py

@@ -74,6 +74,18 @@ def get_selectable(self):
                     courts.append(Court(court))
         return courts
 
+    def get_selectable_groups(self):
+        groups = []
+        for category in self._data:
+            courts = [
+                Court(court)
+                for court in category.get("courts")
+                if court.get("selectable")
+            ]
+            if len(courts) > 0:
+                groups.append(CourtGroup(category.get("display_name"), courts))
+        return groups
+
     def get_listable_groups(self):
         groups = []
         for category in self._data:

src/ds_caselaw_utils/test_courts.py

@@ -12,19 +12,31 @@ def test_loads_selectable_courts(self):
         data = [
             {
                 "name": "court_group",
+                "display_name": "court group 1",
                 "courts": [
                     {
                         "name": "court1",
                         "selectable": True,
                     },
                     {"name": "court2", "selectable": False},
                 ],
-            }
+            },
+            {
+                "name": "court_group2",
+                "display_name": "court group 2",
+                "courts": [{"name": "court3", "selectable": False}],
+            },
         ]
         repo = CourtsRepository(data)
         selectable = repo.get_selectable()
         self.assertIn("court1", [c.name for c in selectable])
         self.assertNotIn("court2", [c.name for c in selectable])
+        groups = repo.get_selectable_groups()
+        self.assertIn("court group 1", [g.name for g in groups])
+        self.assertNotIn("court group 2", [g.name for g in groups])
+        self.assertIn("court1", [c.name for g in groups for c in g.courts])
+        self.assertNotIn("court2", [c.name for g in groups for c in g.courts])
+        self.assertNotIn("court3", [c.name for g in groups for c in g.courts])
 
     def test_loads_listable_courts(self):
         data = [