Inconsistent cm:modifier depending on the rendition is supported or not

[howkymike]

I noticed when a code is run with the System security context, the cm:modifier property will be changed to "System" when the thumbnail is generated, or will change to the currently authenticated user when the thumbnail is not generated.

Sample code:

try {
	AuthenticationUtil.setRunAsUserSystem();
	FileUtils.copySourceContent(sourceRef, destRef, contentService); // sample method which copies PROP_CONTENT from sourceRef to destRef using ContentReader and ContentWriter
} finally {
	AuthenticationUtil.clearCurrentSecurityContext();
}

Example No 1. File sample.pdf (pdf is supported by the renditionService) after executing this code as the test user will have cm:modifier set to "System"
Example No 2. File test.dwg (dwg is not supported by the renditionService ) after execution this code as the test user will have cm:modifier set to "test"

When debugging I can see my code is executed as the "test" ( getFullyAuthenticatedUser() ) with the "System" security content ( getRunAsUser() ) BUT the code creating a thumbnail ( processEvent() in the RenditionEventProcessor.java, onContentUpdate(), requestAsyncTransformOrRendition() in the RenditionService2Impl.java, consume(), consumeRendition(),setThumbnailLastModified()) is executed as the "System".

I suppose there is a bug in the 135 line of RenditionEventProcessor.java where we should get the authenticatedUser instead of the executingUser.

The commit introducing this issue: 65a35ba by @cristianturlica
In the RenditionEventProcessor::processEvent() the Context is null so we have to read authenticatedUser and executingUser from the event. Currently only executingUser is read and authenticatedUser is missed