🏷️ Enforce client adapter type in auth exchange

Author: nevans

lib/net/imap/sasl/authentication_exchange.rb

@@ -81,6 +81,7 @@ def self.build(client, mechanism, *args, sasl_ir: true, **kwargs, &block)
         attr_reader :mechanism, :authenticator
 
         def initialize(client, mechanism, authenticator, sasl_ir: true)
+          client => SASL::ClientAdapter
           @client = client
           @mechanism = Authenticators.normalize_name(mechanism)
           @authenticator = authenticator