get rid of pydantic v2>v3 deprication warning; add optional indentation

[gravmatt]

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[CLAassistant]

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[MasterKale]

Thanks for the contribution @gravmatt, unfortunately this library is aiming to support both v1 and v2 for now so the deprecation warnings can't be addressed like this just yet. If you're interested in updating the PR to work with v1 as well I'll still accept it.

[gravmatt]

Hey @MasterKale I understand. webauthn 1.10.1 requires pydantic>=1.10.11. I installed pydantic 1.10.11 and in the helpers > options_to_json.py there is the function options_to_json which uses model_dump_json. This function was introduced in pydantic v2 and is not available in v1.

2b87a8c#diff-b58c7253734137d5c7558d6204ca581688ed2fed8559c83b28bb7741a8c98172

[MasterKale]

@gravmatt Thank you for creating this PR. I've decided to go with #172 because it reduces the library user's exposure to more of the v1/v2 divide. 🙇