Planetmint-cryptoconditions

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* fixed CI issues and dependencies: bumped versions of cryptography, requests

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* fixed copy-paste bug: subfulfillment vs subcondition in threshold.py

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* removed zenroom signing

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* removed automated "keyring" handling from ZenroomSha256.sign method
* improved sample code
* simplified dependency management
* improved github workflows

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* support of the neweste zenroom 2.3.1
* package renaming to be compatible to poetry deyploments and naming conventions

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* Integrated zenroom calling convention as defined in PRP 13 (breaking changes)
* bumped base58 versions
* improved linting
* added audit