TOK-393 Add `Did::get_metadata` tests.
TOK-393 Add `Did::get_metadata` tests.

Signed-off-by: dastardlychimp <db858739152082a3cb8365268ad0cd877ac844f1@evernym.com>

srottem/indy-sdk,anastasia-tarasova/indy-sdk,srottem/indy-sdk,srottem/indy-sdk,anastasia-tarasova/indy-sdk,srottem/indy-sdk,Artemkaaas/indy-sdk,anastasia-tarasova/indy-sdk,anastasia-tarasova/indy-sdk,peacekeeper/indy-sdk,Artemkaaas/indy-sdk,peacekeeper/indy-sdk,peacekeeper/indy-sdk,peacekeeper/indy-sdk,srottem/indy-sdk,srottem/indy-sdk,anastasia-tarasova/indy-sdk,Artemkaaas/indy-sdk,Artemkaaas/indy-sdk,peacekeeper/indy-sdk,srottem/indy-sdk,srottem/indy-sdk,Artemkaaas/indy-sdk,anastasia-tarasova/indy-sdk,anastasia-tarasova/indy-sdk,srottem/indy-sdk,anastasia-tarasova/indy-sdk,Artemkaaas/indy-sdk,anastasia-tarasova/indy-sdk,Artemkaaas/indy-sdk,Artemkaaas/indy-sdk,peacekeeper/indy-sdk,peacekeeper/indy-sdk,peacekeeper/indy-sdk,Artemkaaas/indy-sdk,Artemkaaas/indy-sdk,srottem/indy-sdk,anastasia-tarasova/indy-sdk,srottem/indy-sdk,peacekeeper/indy-sdk,Artemkaaas/indy-sdk,anastasia-tarasova/indy-sdk,peacekeeper/indy-sdk,anastasia-tarasova/indy-sdk,peacekeeper/indy-sdk,peacekeeper/indy-sdk,srottem/indy-sdk,Artemkaaas/indy-sdk,srottem/indy-sdk,Artemkaaas/indy-sdk,peacekeeper/indy-sdk,anastasia-tarasova/indy-sdk