Add SigV4 note to generate_presigned_post documentation

Author: adev-code

botocore/signers.py

@@ -836,6 +836,19 @@ def generate_presigned_post(
 ):
     """Builds the url and the form fields used for a presigned s3 post
 
+    .. note::
+
+        Amazon S3 supports Signature Version 4, a protocol for authenticating 
+        inbound API requests to AWS services, in all AWS Regions. At this time, 
+        AWS Regions created before January 30, 2014, will continue to support 
+        the previous protocol, Signature Version 2. Any new Regions after January 30, 
+        2014, will support only Signature Version 4 and therefore all requests to 
+        those Regions must be made with Signature Version 4.
+
+        For more details, see:
+        `AWS Signature Version 4 <https://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-authenticating-requests.html>`_.
+
+        
     :type Bucket: string
     :param Bucket: The name of the bucket to presign the post to. Note that
         bucket related conditions should not be included in the