Response Signated Signed-ness can flip when xml is read

[Fusty]

The value of samlResponse.isSigned() before this line is true

https://github.com/dotCMS/plugin-com.dotcms.dotsaml/blob/4.0-4.3.x/src/com/dotcms/plugin/saml/v3/handler/HttpPostAssertionResolverHandlerImpl.java#L94

After this line it is false.

This may be because I am logging at the DEBUG level.

I just ran into this while setting up a Google G-Suite Apps SAML IdP.

The fix is to verify the response signature before assertion xml is converted to an object. I'm not certain why this occurs, but it is consistent in my current environment and this tiny tweak fixes it.

[Fusty]

@gabbydotCMS I have prepared a branch with the minimal fix required to accommodate this situation.

https://github.com/dotCMS/plugin-com.dotcms.dotsaml/tree/ethode/response-signedness-flips-when-read