feat(calendar): single Default personal with guards and backfill

Ensure title Default; reject second personal and delete/type-change of
the sole personal; migrate extras to commercial or soft-delete.

Refs EventHub/EventHubBack#64

src/handlers/handler_calendar_by_id.erl

@@ -152,6 +152,8 @@ update_calendar(Req) ->
               handler_utils:send_error(Req2, 403, <<"Access denied">>);
             {error, subscription_required} ->
               handler_utils:send_error(Req2, 402, <<"Subscription required for commercial calendar">>);
+            {error, default_calendar} ->
+              handler_utils:send_error(Req2, 403, <<"default_calendar">>);
             {error, not_found} ->
               handler_utils:send_error(Req2, 404, <<"Calendar not found">>);
             {error, {invalid_settings, Key}} when is_binary(Key) ->
@@ -176,6 +178,8 @@ delete_calendar(Req) ->
       case logic_calendar:delete_calendar(UserId, CalendarId) of
         {ok, _} ->
           handler_utils:send_json(Req1, 200, #{status => <<"deleted">>});
+        {error, default_calendar} ->
+          handler_utils:send_error(Req1, 403, <<"default_calendar">>);
         {error, access_denied} ->
           handler_utils:send_error(Req1, 403, <<"Access denied">>);
         {error, not_found} ->

src/handlers/handler_calendars.erl

@@ -140,6 +140,8 @@ create_calendar(Req) ->
                   handler_utils:send_json(Req2, 201, Response);
                 {error, subscription_required} ->
                   handler_utils:send_error(Req2, 402, <<"Subscription required for commercial calendar">>);
+                {error, personal_exists} ->
+                  handler_utils:send_error(Req2, 409, <<"personal_exists">>);
                 {error, user_inactive} ->
                   handler_utils:send_error(Req2, 403, <<"User account is not active">>);
                 {error, {content_banned, _Words}} ->