rabbit_khepri: Unregister all projections when enabling khepri_db ff

Author: the-mikedavis

deps/rabbit/src/rabbit_khepri.erl

@@ -1095,6 +1095,12 @@ collect_payloads(Props, Acc0) when is_map(Props) andalso is_list(Acc0) ->
               Acc
       end, Acc0, Props).
 
+-spec unregister_all_projections() -> Ret when
+      Ret :: ok | timeout_error().
+
+unregister_all_projections() ->
+    khepri:unregister_projections(?STORE_ID, all).
+
 register_projections() ->
     RegFuns = [fun register_rabbit_exchange_projection/0,
                fun register_rabbit_queue_projection/0,
@@ -1507,6 +1513,7 @@ get_feature_state(Node) ->
 khepri_db_migration_enable(#{feature_name := FeatureName}) ->
     maybe
         ok ?= sync_cluster_membership_from_mnesia(FeatureName),
+        ok ?= unregister_all_projections(),
         ok ?= register_projections(),
         migrate_mnesia_tables(FeatureName)
     end.