[IMP] attachment_s3: Consider bin_size context key

When bin_size context key is set, read operations on attachments
are supposed to return the size of the attachment and not its content

attachment_s3/models/ir_attachment.py

@@ -122,6 +122,8 @@ class IrAttachment(models.Model):
                 bucket.meta.client.head_object(
                     Bucket=bucket.name,  Key=key
                 )
+                if bin_size:
+                    return bucket.Object(key).content_length
                 res = io.BytesIO()
                 bucket.download_fileobj(key, res)
                 res.seek(0)