Fix: Parse as text for non-binary payload

[willempardaens]

When using tools such as Postman or curl to send events to AEM, payload is sent as normal text/json and not as binary. So on the receiver side (plugin) it has to be treated as such. See https://community.solace.com/t/weird-chars-at-start-of-text-payload/1856.

When using getBinaryAttachment() on a string payload, you will get the following:

Sending:
{ "foo":"bar" }

Receiving:
" N{ \"foo\":\"bar\" }"

With 2 invalid characters in the beginning, which are payload-length identifiers from the Structured Data Type (SDT) formatted message.

[sjvans]

lgtm. @David-Kunz, please review as well.