hotspots: Add backend support for tutorial hotspots.

This commit adds the backend support for a new style of tutorial which
allows for highlighting of multiple areas of the page with hotspots that
disappear when clicked by the user.

zerver/lib/hotspots.py

@@ -0,0 +1,12 @@
+from zerver.models import UserProfile, UserHotspot
+
+from typing import List, Text
+
+ALL_HOTSPOTS = ['welcome', 'streams', 'topics', 'narrowing', 'replying', 'get_started']
+def get_next_hotspots(user):
+    # type: (UserProfile) -> List[Text]
+    seen_hotspots = frozenset(UserHotspot.objects.filter(user=user).values_list('hotspot', flat=True))
+    for hotspot in ALL_HOTSPOTS:
+        if hotspot not in seen_hotspots:
+            return [hotspot]
+    return []