[All SDKs] support OAuth2 scopes for authentication

[le-yams]

Description

Current SDKs only support Auth0's client credentials flow implementation.

In order to also support standard OAuth2 client credentials flow, the audience parameter should be made optional and another optional scope parameter should be added.

SDKs to be updated

• [ ] JS SDK
• [x] Go SDK (https://github.com/openfga/sdk-generator/pull/256, https://github.com/openfga/go-sdk/pull/62)
• [ ] .NET SDK
• [ ] Python SDK
• [x] Java SDK (#257)