Finolog-sdk

Added
- add `FinologCountryService`
- add return `bool` in `get_or_create_by_inn`

Added
- add `FinologRequisiteService`
- add `get_or_create_by_inn` in `FinologContractorService`
- add `validate_string_length`

Added
- add payload validation
- add `ValidationError`
- implemented `create_contractor` method
- implemented `update_contractor` method

Changed
- move client to `client.py`

Removed
- `__validate_contractor_id` method

Changed
- minor changes

Added
- Project