Add envs for Indexer.Utils.NotificationsCleaner (#418)

* Add envs for Indexer.Utils.NotificationsCleaner

* Update setup/env-variables/backend-env-variables.md

Co-authored-by: Victor Baranov <[email protected]>

---------

Co-authored-by: Victor Baranov <[email protected]>

Author: nikitosing

setup/env-variables/backend-env-variables.md

@@ -202,6 +202,9 @@ _**Note**_**: Before release 5.1.2, all environment variables of time format sup
 | `ETHEREUM_JSONRPC_GETH_ALLOW_EMPTY_TRACES`                    | Allow transactions to not have internal transactions. Implemented in [#10200](https://github.com/blockscout/blockscout/pull/10200)                                                                                                                                                                                                                                                                                                                                                                                               | <p>Version: v6.8.0+<br>Default: <code>false</code><br>Applications: Indexer</p>                                      |
 | `INDEXER_DISABLE_REPLACED_TRANSACTION_FETCHER`                | If `true`, `Indexer.Fetcher.ReplacedTransaction` fetcher doesn't run.                                                                                                                                                                                                                                                                                                                                                                                                                                                            | <p>Version: v6.8.0+<br>Default: <code>false</code><br>Applications: Indexer</p>                                      |
 | `INDEXER_INTERNAL_TRANSACTIONS_FETCH_ORDER`                   | Order of fetching internal transactions from node. Possible values: `asc`, `desc`. Implemented in [#10912](https://github.com/blockscout/blockscout/pull/10912)                                                                                                                                                                                                                                                                                                                                                                  | <p>Version: v6.9.0+<br>Default: <code>asc</code><br>Applications: Indexer</p>                                        |
+| `INDEXER_DB_EVENT_NOTIFICATIONS_CLEANUP_ENABLED`                       | If `true`, `Indexer.Utils.EventNotificationsCleaner` process starts. Implemented in [#12738](https://github.com/blockscout/blockscout/pull/12738)                                                                                                                                                                                                                                                                                                                                                                                     | <p>Version: master<br>Default: <code>true</code><br>Applications: Indexer</p>                                        |
+| `INDEXER_DB_EVENT_NOTIFICATIONS_CLEANUP_INTERVAL`                      | Interval between DB event notifications cleanup. [Time format](backend-env-variables.md#time-format). Implemented in [#12738](https://github.com/blockscout/blockscout/pull/12738)                                                                                                                                                                                                                                                                                                                                                        | <p>Version: master<br>Default: <code>2m</code><br>Applications: Indexer</p>                                          |
+| `INDEXER_DB_EVENT_NOTIFICATIONS_CLEANUP_MAX_AGE`                       | Max age of DB event notifications before they are cleaned up. [Time format](backend-env-variables.md#time-format). Implemented in [#12738](https://github.com/blockscout/blockscout/pull/12738)                                                                                                                                                                                                                                                                                                                                           | <p>Version: master<br>Default: <code>5m</code><br>Applications: Indexer</p>                                          |
 
 ## <mark style="background-color:orange;">DB Migrations & Sanitizer Management</mark>