Help with running indexer

[fabrice]

@cryptoland

Which parameters and values should be in config.json file, so that
-Archival mode can stop
-The mainnet data can continue to sync from the last block that has been retrieved
-Also the indexer can be started

The only official way of using indexer with a node is to always keep the node archival.
In the past, some upgrades of the indexer required re-indexing all the blocks.