Implement token validation & authorization

[OSchlienz]

Implement required checks for AT and SI-Token:

• SI-Token2 (external Token) https://github.com/eclipse-tractusx/identity-trust/blob/main/specifications/M1/identity.protocol.base.md#42-validating-self-issued-id-tokens
• Access Token (internal token): signature
• RequestorVP/signatureSI-Token2 = audience in AT

https://github.com/eclipse-tractusx/managed-identity-wallet/blob/develop/docs/arc42/images/VVP-Flow.puml

[borisrizov-zf]

@aleksandra-bel welcome, this would be a good starting point, after you've become familiar with the code.

[borisrizov-zf]

@andreibogus welcome, this would be a good starting point, after you've become familiar with the code.

[borisrizov-zf]

@aleksandra-bel @andreibogus fyi