MT#8287 only create aliases if available on subscriber creation

some input validation, fixes issues on subadmin subscriber creation

(cherry picked from commit c15acb942384c7a1847a225346a0bc6a54e9d8fa)
(cherry picked from commit b8b762d8f7be3bfe283cd1a0153a04f2e7128820)
MT#8287 fix subscriber termination by subadmin

(cherry picked from commit ef713a8f843cd8b54b2f40b9f4ecd87a78b1674b)
(cherry picked from commit 443a84db475f224c2b28827c67055ee6c9d2e26c)