fix: pass JWK for singing so that KeyID is set in JWTs

[mitar]

It is harder to validate generated JWTs because currently they do not include a key ID in the header. Even when key ID exists in the JWK used for signing. The reason is that Fosite currently removes this metadata information, but it is not necessary to remove it, our signing library uses it and knows how to use JWKs, even more, it adds key ID automatically if it is available and provided with a JWK.

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