OIDC tools

[peppelinux]

in the onboarding frontend we need some tools to

• [x] create a jwk
• [x] convert a PEM certificate/key to private/public jwk
• [x] create a trust chain by submitting only a sub
• [x] validating a trust mark
• [x] decode a jwt and verify if a jwk is also submitted

[peppelinux]

Done here https://github.com/peppelinux/spid-cie-oidc-django/pull/67