Add clientAuthorizationType property to Security Scheme Object

[MugeSo]

Background

RFC6749 allows authorization server to implement client authentication, which is used when a credential client access to token endpoint.

If the client type is confidential, the client and authorization
server establish a client authentication method suitable for the
security requirements of the authorization server. The authorization
server MAY accept any form of client authentication meeting its
security requirements.

RFC6749 also describes 2 typical client authentication method in §2.3.1.
However it allows any other suitable HTTP authentication scheme in §2.3.2

Proposal

To follow this spec, I propose to add a `clientAuthorizationType' property to Security Scheme Object.

OR

Add clientAuthorization property which is an Object like Security Scheme Object.

[lornajane]

Since this issue hasn't had much interaction or engagement, it will be closed.