docs: update notes on data connector test files

Author: ivan-p92

docs/03-quickstart/01-streaming/04-receiving-data/02-exporting-keys.md

@@ -151,7 +151,8 @@ $ aws s3 cp s3://strmprivacy-export-demo/perf-test-keys/2021-05-04T14:13:00-keys
 ```
 1. `.strm_test...95-dfec21be8251.jsonl`: This is a test file created by STRM Privacy to verify that the exporter can
     actually write in this bucket. Because it starts with a `.` it is
-    ignored by most tools.
+    ignored by most tools. If the data connector used has delete
+    permissions, this file will be deleted after the test and therefore absent.
 2. `2021-05-04T14:13:00-keys-e1...-7-8-9.csv`: Because the interval is 30 seconds, a file is written every 30
     seconds. Each file contains JSONL with one key per line. The
     line contains both a `keyLink` attribute, with the key link of the

docs/03-quickstart/03-data-connectors/01-s3.md

@@ -112,6 +112,7 @@ aws iam create-access-key --user-name strm-export-demo > s3.json
 STRM Privacy validates the user and credentials configuration by writing an empty JSONL file
 (file name: `.strm_test_<random UUID>.jsonl`) to the specified
 bucket/prefix upon creation of the batch exporter.
+If the data connector used has delete permissions, this file will be deleted after the test and therefore absent.
 :::
 
 First, make sure you have a file named `s3.json` in your current