Further refactored based on MR review

.gitlab-ci.yml

notification-acceptance-test/docs/README.md

notification-acceptance-test/pom.xml

.../opengroup/osdu/notification/api/TestPushEndpointGsa.java

...opengroup/osdu/notification/api/TestPushEndpointHMAC.java

...rg/opengroup/osdu/notification/util/BaseTestTemplate.java

...est/java/org/opengroup/osdu/notification/util/Config.java

...group/osdu/notification/util/DecodedContentExtractor.java

.../java/org/opengroup/osdu/notification/util/FileUtils.java

...java/org/opengroup/osdu/notification/util/HttpClient.java

...a/org/opengroup/osdu/notification/util/ServicesUtils.java

...t/java/org/opengroup/osdu/notification/util/TestBase.java

.../java/org/opengroup/osdu/notification/util/TestUtils.java

.../org/opengroup/osdu/notification/util/TokenTestUtils.java