Merge cardano x402 into v2-development

[fabianbormann]

We are adding this as a draft PR first. The draft status will be removed after internal alignments.

Description

This PR adds the exact schema for Cardano to allow an integration of x402 with the Cardano blockchain.

Checklist

• [X] I have formatted and linted my code
• [X] All new and existing tests pass
• [X] My commits are signed (required for merge)

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