Fix bug: Return empty access_keys object when access keys do not exist (

#1309)

While running the AWS sync in Cartography, the following error occurs,
causing the sync process to fail:

```
ERROR:cartography.sync:Unhandled exception during sync stage 'aws'
Traceback (most recent call last):
  File "/home/REDACTED/cartography/cartography/sync.py", line 113, in run
    stage_func(neo4j_session, config)
  File "/home/REDACTED/cartography/cartography/util.py", line 197, in timed
    return method(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/REDACTED/cartography/cartography/intel/aws/__init__.py", line 298, in start_aws_ingestion
    sync_successful = _sync_multiple_accounts(
                      ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/REDACTED/cartography/cartography/intel/aws/__init__.py", line 169, in _sync_multiple_accounts
    _sync_one_account(
  File "/home/REDACTED/cartography/cartography/intel/aws/__init__.py", line 64, in _sync_one_account
    RESOURCE_FUNCTIONS[func_name](**sync_args)
  File "/home/REDACTED/cartography/cartography/util.py", line 197, in timed
    return method(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/REDACTED/cartography/cartography/intel/aws/iam.py", line 819, in sync
    sync_user_access_keys(neo4j_session, boto3_session, current_aws_account_id, update_tag, common_job_parameters)
  File "/home/REDACTED/cartography/cartography/util.py", line 197, in timed
    return method(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/REDACTED/cartography/cartography/intel/aws/iam.py", line 795, in sync_user_access_keys
    access_keys = get_account_access_key_data(boto3_session, user["name"])
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/REDACTED/cartography/cartography/util.py", line 197, in timed
    return method(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/REDACTED/cartography/cartography/intel/aws/iam.py", line 230, in get_account_access_key_data
    for access_key in access_keys['AccessKeyMetadata']:
                      ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^
KeyError: 'AccessKeyMetadata'
ERROR:__main__:Error in AWS account sync REDACTED: 'AccessKeyMetadata'
```
The fix involves returning the access_keys object directly from the
get_account_access_key_data function. This ensures that the function
returns the correct data structure, even if the AccessKeyMetadata key is
missing.

The function was tested with various AWS accounts to ensure it correctly
handles cases where the AccessKeyMetadata key is present and when it is
missing.
Verified that the sync process was completed successfully without any
errors.

Co-authored-by: Alex Chantavy <[email protected]>

cartography/intel/aws/iam.py

@@ -227,6 +227,7 @@ def get_account_access_key_data(boto3_session: boto3.session.Session, username:
         logger.warning(
             f"Could not get access key for user {username} due to NoSuchEntityException; skipping.",
         )
+        return access_keys
     for access_key in access_keys['AccessKeyMetadata']:
         access_key_id = access_key['AccessKeyId']
         last_used_info = client.get_access_key_last_used(