Implement signature calculation and verification in application scope

[romanstrobl]

Description

Implement signature calculation and verification in application scope for both standard and JWT endpoints:

• /rest/v4/dsa/sign
• /rest/v4/dsa/verify
• /rest/v4/jws/sign
• /rest/v4/jws/verify

Acceptance criteria

Added support for signature calculation and verification in application scope.

Technical specification

Use applicationKey as identification of application.

QA specification

Tested by unit tests.