update docs

Author: zvonand

docs/en/sql-reference/table-functions/s3.md

@@ -276,15 +276,26 @@ For example, if the provided credentials have permission to assume a role but la
 
 For more details on role assumption, read [AWS AssumeRole documentation](https://docs.aws.amazon.com/STS/latest/APIReference/API_AssumeRole.html).
 
-To assume a role, pass `roleARN` via the `extra_credentials` parameter to the `s3` function. Example:
+To enable role assumption, pass parameters via the extra_credentials argument in the s3 function. The following keys are supported:
+
+* `role_arn` (required) — ARN of the IAM role to assume. **If this key is not provided, ClickHouse will not attempt to assume a role and will use the original credentials as-is.**
+* `role_session_name` (optional) — Custom session name to include in the AssumeRole request.
+* `sts_endpoint_override` (optional) — Overrides the default AWS STS endpoint (https://sts.amazonaws.com). Useful for testing with a mock or when using another STS-compatible service.
 
 ```sql
-SELECT count() FROM s3('<s3_bucket_uri>/*.tsv',access_key_id,secret_access_key,'CSVWithNames',extra_credentials(role_arn = 'arn:aws:iam::111111111111:role/BucketAccessRole-001'))
+SELECT count() FROM s3(
+    '<s3_bucket_uri>/*.csv',
+    access_key_id,
+    secret_access_key,
+    'CSVWithNames',
+    extra_credentials(
+        role_arn = 'arn:aws:iam::111111111111:role/BucketAccessRole-001',
+        role_session_name = 'ClickHouseSession',
+        sts_endpoint_override = 'http://mock-sts:8080'
+    )
+)
 ```
 
-It is also possible to pass `role_session_name` inside `extra_credentials` if needed.
-
-
 ## Working with archives
 
 Suppose that we have several archive files with following URIs on S3: