Env var ENABLE_DATETIME_INDEX_FILTERING="false" evaluated as truthy in bulk insert

[alambare]

Describe the bug
Setting the environment variable ENABLE_DATETIME_INDEX_FILTERING to " false" is evaluated as truthy in the bulk insert item endpoint.

The bug is caused by https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/blob/main/stac_fastapi/core/stac_fastapi/core/core.py#L1432 that uses os.getenv() instead of the get_bool_env() function.

To Reproduce

Enable the BulkTransactionExtension and set ENABLE_DATETIME_INDEX_FILTERING="false"

Expected behavior

"false" should be considered as false.

[jonhealy1]

Hi @alambare. Thanks for opening this issue. Would you like to make a pr for this change?

[alambare]

Hello @jonhealy1,
I just create the PR