Unit tests for app-common

Changes in this Pull Request:

Mandatory checks:

[x] latest changes were fetched from the upstream branch before creating this PR (branch is up to date)
[ ] changes were tested manually
[x] unit tests were properly implemented
[ ] communication about interdependent changes has been sent to the team (if applicable)
[ ] respective Jenkins jobs were referenced in additional context section of this PR

OSCM Build References: N/A

This change is

servicecatalog / oscm-app