Fix sonar issues in PAP
Replace string concatenation with "{}" place-holders in logging
statements.
Refactored PdpStatusMessageHandler and PdpGroupStateChangeProvider
to extract common/duplicate code block into PdpMessageGenerator.
Refactored selectPdpGroupsForRegistration() to reduce "cyclomatic complexity";
extracted selectPdpSubGroupsForRegistration from it.
Issue-ID: POLICY-1791
Signed-off-by: jrh3 <jrh3@att.com>
Change-Id: Ia0ebc1cf41cd2fa288130b4a58614a4983f47f8b
Signed-off-by: jrh3 <jrh3@att.com>