merge STF678_Task1_MEC021 into STF678_Task4

update etsi mec sandbox mec 021 AMS front-end file as per 3.1.1 AMS document version and merge request for STF678_Task1_MEC021 into STF678_Task4

requested review from @ayesha.ayub

assigned to @ikram.haq

mentioned in commit b1db10fd

merged