Add signer tests for verifying presentation

Added due to update of the Signer service to verify presentations.
Verifying credential is not needed at the moment and this is the reason it is not fully functioning.
The negative tests are WIP due to bug

requested review from @rosen.georgiev

added 1 commit

• 5c9da73f - cleanup imports

Compare with previous version

mentioned in commit 1a07b6c8

merged