Feature Add structured address fields and deprecate legacy address field

[kaspernowak]

Summary

Implements support for bexio’s upcoming structured address requirements by introducing street_name, house_number, and address_addition fields to all relevant DTOs. The legacy address property is marked as deprecated with runtime warnings and could be removed after 2025-12-07.

Details

Structured Address Fields

• Adds street_name, house_number, and address_addition to all DTOs handling contact and additional address data.
• Ensures all request logic and tests use the new structured fields, aligning with future API requirements.

Deprecation Notice

• The legacy address property is retained for backward compatibility but now triggers runtime deprecation warnings.
• Planned removal after 2025-12-07.

Documentation

• Updates documentation to reflect the new address structure.

Compatibility

• All changes are forward-compatible with bexio’s announced API updates.

closes #28

[StanBarrows]

@kaspernowak
We’ve just completed the OAuth PR and will take a closer look at this in the coming weeks.

[kaspernowak]

@StanBarrows Thank you!
@RhysLees Since the breaking change won't happen before December, I think it would be better to look at #32 before this.