Syntax Fix for Role Check

Fixes a syntax issue for the role check function doesPayloadSatisfyRoleRequirement($payload).

Level clarification:

function doesPayloadSatisfyRoleRequirement($payload)

to

private function doesPayloadSatisfyRoleRequirement($payload)

and a $this-> object specifier

$satisfiesRoleRequirement = doesPayloadSatisfyRoleRequirement($payload);

to

$satisfiesRoleRequirement = $this->doesPayloadSatisfyRoleRequirement($payload);