Add support for more common Auth methods.

[loechel]

httpx is a fantastic library for doing http request operations and implement REST APIs.

REST APIs rely on Authentication methods to grant access for services.

Two documentations add the reference for most basic authentication methods that a library should provid:

• mdn Developer Documentation - HTTP authentication
• openAPI Specification - 4.27 Security Scheme Object

Therefore an additional Auth methods should be provided by httpx beside the already given (Basic, Digest and NetRC):

• Bearer (RFC 6750)

Additional higher Level Authentication Protocols should go into the third-party addon httpx-auth:

• SAML / SAML2
• OAuth 2.0 Flow
• OpenID Connect Flow
• MutalTLS