BeginAuthHandler will redirect the user to the appropriate authentication end-point for the requested provider.

It expects to be able to get the name of the provider from the query parameters as either "provider" or ":provider".

I would recommend using the BeginAuthHandler instead of doing all of these steps yourself, but that's entirely up to you.

GetFromSession retrieves a previously-stored value from the session.

Logout invalidates a user session.

SetStore sets the store for the gothic session.

Store returns the store for the gothic session.

StoreInSession stores a specified key/value pair in the session.

GetProviderName is a function used to get the name of a provider for a given request.

GetState gets the state returned by the provider during the callback.

SetState sets the state string associated with the given request.