The user-specified message attribute value. For string data types, the value attribute has the same restrictions on the content as the message body. For more information, see
Publish.
Name, type, and value must not be empty or null. In addition, the message body should not be empty or null. All parts of the message attribute, including name, type, and value, are included in the message size restriction, which is currently 256 KB (262,144 bytes). For more information, see Using Amazon SNS Message Attributes.
