Document permissions requirements for s3 source

Author: treff7es

metadata-ingestion/docs/sources/s3/s3_pre.md

@@ -0,0 +1,37 @@
+### Prerequisites
+
+To allow the S3 ingestion source ingest metadata from an S3 bucket, you need to grant the necessary permissions to an IAM user or role. Follow these steps:
+
+1. **Create an IAM Policy**: Create a policy that grants read access to the S3 bucket.
+
+```json
+{
+  "Version": "2012-10-17",
+  "Statement": [
+    {
+      "Sid": "VisualEditor0",
+      "Effect": "Allow",
+      "Action": [
+        "s3:ListBucket",
+        "s3:GetBucketLocation",
+        "s3:GetObject"
+      ],
+      "Resource": [
+        "arn:aws:s3:::your-bucket-name",
+        "arn:aws:s3:::your-bucket-name/*"
+      ]
+    }
+  ]
+}
+```
+
+**Permissions Explanation**:
+- `s3:ListBucket`: Allows listing the objects in the bucket. This permission is necessary for the S3 ingestion source to know which objects are available to read.
+- `s3:GetBucketLocation`: Allows retrieving the location of the bucket.
+- `s3:GetObject`: Allows reading the actual content of the objects in the bucket. This is needed to infer schema from sample files.
+
+
+2. **Attach the Policy to an IAM User or Role**: Attach the created policy to the IAM user or role that the S3 ingestion source will use.
+
+
+3. **Configure the S3 Ingestion Source**: Configure the user in s3 ingestion who you attached the role above.