replace discarded term in code with delete candidate

[vohmar]

There is a term discarded used in the code to mark domains that have deleteCandidate status set. As discarded term is not used anywhere in the business processes it creates a confusion about meaning of it.

It is a good practice to use same terminology in software as is used in business processes. Therefore term discarded should be replaced with delete candidate term as this is one that is used to describe domains waiting for the deletion to happen.

introduced with: #789

[artur-intech]

This is not a bug. The naming was my decision as a part of my job to accomplish the task I have been assigned. If you're not happy with the terms, it would be great to hear your questions and suggestions (about naming).

Anyway, below I explained why this name was needed.

#784 (comment)
#790 (comment)
#792 (comment)