dynamically generated notifs

Some of the notifications can be extracted from DB tables with SQL query. This allows us to avoid redundancy and save db space.

hive/db/db_state.py

@@ -115,6 +115,9 @@ class DbState:
             'hive_votes_voter_id_idx',
             'hive_votes_block_num_idx',
 
+            'hive_subscriptions_block_num_idx',
+            'hive_communities_block_num_idx',
+
             #'hive_posts_cache_ix6a', # (sc_trend, post_id, paidout=0)
             #'hive_posts_cache_ix6b', # (post_id, sc_trend, paidout=0)
             #'hive_posts_cache_ix7a', # (sc_hot, post_id, paidout=0)