Implement JWT decoding and validation for the Provider struct

[nanderstabel]

Description

We will implement JWT decoding and validation for the Provider struct. This will involve decoding the JWT and verifying its signature to ensure its authenticity. Additionally, we will perform other validation checks such as checking the issuer and audience claims.

Motivation

When a SiopRequest is particularly large (for example when it includes a Presentation Definition for Verifiable Presentations, or many claims) a Relying Party may choose to send its request by value by utilizing the request_uri. The actual SiopRequest that can be retrieved by following this redirect uri may or may not be encoded as a JWT. Therefore, the Provider should be capable of decoding and validation JWT's

Resources

SIOPv2 section 9.

To-do List

• Support JWT validation for the Provider struct.