Security Lake Integration should support cross-account

[kclinden]

Is your feature request related to a problem? Please describe.
The 4.9.0 security lake integration currently assumes that the lambda function is running from the same account as AWS Security Lake. This should be ran from a different account the Lambda role should assume the Security Lake created role with an external id.

Describe the solution you'd like
Enhance the Security Lake integration to support cross account

Describe alternatives you've considered
Run the lambda in the same account as security lake which is not recommended by the AWS Security Reference Architecture

Additional context
Source - https://github.com/wazuh/wazuh-indexer/blob/4.9.0/integrations/amazon-security-lake/src/lambda_function.py#L50

[QU3B1M]

Update Security Lake integration to support cross-account, it is not mandatory but it will raise the warning Cross-account access is not being used. Lambda will run with default credentials from the same account. when not running from a different account.

Unit tests were implemented to validate this script functions

% pytest -v                                     
===================================================== test session starts =====================================================
platform darwin -- Python 3.13.0, pytest-8.3.4, pluggy-1.5.0 -- /Users/quebim_wz/IdeaProjects/wazuh-indexer/integrations/amazon-security-lake/venv/bin/python3.13
cachedir: .pytest_cache
rootdir: /Users/quebim_wz/IdeaProjects/wazuh-indexer/integrations/amazon-security-lake/tests
configfile: pytest.ini
collected 7 items                                                                                                             

test_lambda_function.py::test_lambda_handler PASSED                                                                     [ 14%]
test_lambda_function.py::test_assume_role PASSED                                                                        [ 28%]
test_lambda_function.py::test_get_s3_client PASSED                                                                      [ 42%]
test_lambda_function.py::test_get_events PASSED                                                                         [ 57%]
test_lambda_function.py::test_write_parquet_file PASSED                                                                 [ 71%]
test_lambda_function.py::test_upload_to_s3 PASSED                                                                       [ 85%]
test_lambda_function.py::test_get_full_key PASSED                                                                       [100%]

====================================================== 7 passed in 0.92s ======================================================