class Net::IMAP::SASL::XOAuth2Authenticator

See Net::IMAP::SASL::OAuthBearerAuthenticator.
“OAUTHBEARER”, it is still very widely supported.
Although this mechanism was never standardized and has been obsoleted by
documentation for their scopes.
these scopes are not standardized—consult each service provider’s
with the appropriate OAuth2 scopes to access the user’s services. Most of
This mechanism requires an OAuth2 access token which has been authorized<br><br>Microsoft.
and
XOAUTH2 has been documented by
originally created for GMail and widely adopted by hosted email providers.
Authenticator for the “XOAUTH2” SASL mechanism. This mechanism was

def build_oauth2_string(username, oauth2_token) 

def build_oauth2_string(username, oauth2_token)
  format("user=%s\1auth=Bearer %s\1\1", username, oauth2_token)
end

def done?; @done end

does *not* indicate success.
The authentication should not succeed unless this returns true, but it

Returns true when the initial client response was sent. 
def done?; @done end

def initial_response?; true end

+XOAUTH2+ can send an initial client response.

initial_response? -> true
:call-seq: 
def initial_response?; true end

def initialize(user = nil, token = nil, username: nil, oauth2_token: nil,

Any other keyword parameters are quietly ignored.

the service for #username.
* #oauth2_token --- An OAuth2.0 access token which is authorized to access

authenticated identity is established for the client with the OAuth token.
_authorization_ identity and not the _authentication_ identity. The
Note that, unlike some other authenticators, +username+ sets the

#authzid --- an alias for #username.

* #username --- the username for the account being accessed.

=== Properties

and Yahoo[https://senders.yahooinc.com/developer/documentation].
Microsoft[https://learn.microsoft.com/en-us/exchange/client-developer/legacy-protocols/how-to-authenticate-an-imap-pop-smtp-application-by-using-oauth]
Google[https://developers.google.com/gmail/imap/xoauth2-protocol],
Creates an Authenticator for the "+XOAUTH2+" SASL mechanism, as specified by

new(authzid:, oauth2_token:, **) -> authenticator
new(username:, oauth2_token:, **) -> authenticator
new(username, oauth2_token, **) -> authenticator
:call-seq: 
def initialize(user = nil, token = nil, username: nil, oauth2_token: nil,
               authzid: nil, secret: nil, **)
  @username = authzid || username || user or
    raise ArgumentError, "missing username (authzid)"
  @oauth2_token = oauth2_token || secret || token or
    raise ArgumentError, "missing oauth2_token"
  @done = false
end

def process(_data)

with the +oauth2_token+.
Returns the XOAUTH2 formatted response, which combines the +username+ 
def process(_data)
  build_oauth2_string(@username, @oauth2_token)
ensure
  @done = true
end