test(jans-cedarling): add tests and fix bugs caught in testing

[rmarinn]

Is your feature request related to a problem? Please describe.

Certain scenarios that should be considered invalid are incorrectly marked as valid in the JwtValidation process. This can lead to security vulnerabilities and unexpected behavior in the application.

Describe the solution you'd like

Enhance the test suite to ensure comprehensive coverage for all edge cases related to JWT validation. Specifically, the tests should verify that invalid tokens are correctly identified and flagged as such. The following cases should be included:

Access Token

• success if the signature of the access_token is valid
• fail if the signature of the access_token is NOT valid
• fail if token is missing any of these claims: iss, aud, sub, exp
• fail if token is expired
• fail if token is used before nbf

ID Token

• success if the iss of the id_token is the same as the access_token
• success if the aud of the id_token is the same as the access_token
• success if the signature of the id_token is valid
• fail if the iss of the id_token is NOT the same as the access_token
• fail if the aud of the id_token is NOT the same as the access_token
• fail if the signature of the id_token is NOT valid
• fail if token is missing any of these claims: iss, aud, sub, exp
• fail if token is expired
• fail if token is used before nbf

Userinfo Token

• success if the iss of the userinfo_token is the same as the access_token
• success if the aud of the userinfo_token is the same as the access_token
• success if the sub of the userinfo_token is the same as the id_token
• success if the signature of the userinfo_token is valid
• fail if the iss of the userinfo_token is NOT the same as the access_token
• fail if the aud of the userinfo_token is NOT the same as the access_token
• fail if the sub of the userinfo_token is NOT the same as the id_token
• fail if the signature of the userinfo_token is NOT valid
• fail if token is missing any of these claims: iss, aud, sub, exp
• fail if token is expired
• fail if token is used before nbf

Key Service

• success if the KeyService can update it's local keystore
• fail if KeyService cannot fetch openid configuration from openid_configuration_uri
• fail if KeyService cannot fetch JWKS from jwks_uri