For OAuth2 Basic，I think it is better to delete AuthStyle: oauth2.AuthStyleInParams

[xin053]

https://github.com/apache/incubator-answer-plugins/blob/743ff5036d5b2b8ffa4c38c9ac8aaa380a79c648/connector-basic/basic.go#L105

if you specify oauth2.AuthStyleInParams，ClientID and ClientSecret will be added as client_id and client_secret in params of the request，but if the server wants the clientID & clientSecret in a different form，such as Basic Authorization，the ConnectorReceiver will failed with connector received failed, error info: code exchange failed: oauth2: cannot fetch token: 401 Unauthorized

however, if we delete AuthStyle: oauth2.AuthStyleInParams，ConnectorReceiver will first try AuthStyleInHeader such as Basic Authorization; if failed, then try AuthStyleInParams(client_id and client_secret params)

refer to: https://github.com/golang/oauth2/blob/4c91c17b32051e551fc27bdbdea4edc060b0aae5/internal/token.go#L212

[LinkinStars]

Done in v1.2.5