2.9.1

Changed

• Adapt authorize_account flow to multi-bucket keys.
• Migrate to b2 native api v4.
• Move url_for_api func to an internal classmethod in B2Api class.
• Release apiver v3 interface. from b2sdk.v3 import ... is now the recommended import, but previous versions are still supported.
• Update application key classes to support multiple bucket ids.
• Update create_key flow to multi-bucket keys.

Infrastructure

• Migrate integration tests to apiver v3.