ParseKey converts the binary contents of a private key file to an *rsa.PrivateKey.

RegisterBrokenAuthHeaderProvider previously did something.

ResetAuthCache resets the global authentication style cache used for AuthStyleUnknown token requests.

HTTPClient is the context key to use with golang.org/x/net/context's WithValue function to associate an *http.Client value with a context.

ContextKey is just an empty struct.

ParamsConf describe the config for params purpose to change name of params which not is `client_id` or `client_secret` other providers not follow the oauth2 standard, such as Zalo Social API.

Token represents the credentials used to authorize the requests to access protected resources on the OAuth 2.0 provider's backend.

AuthStyle is a copy of the github.com/huynhsamha/oauth2 package's AuthStyle type.