track channel registrations per account

* limit the total number of registrations per account
* when an account is unregistered, unregister all its channels

irc/config.go

@@ -181,7 +181,8 @@ type NickReservationConfig struct {
 
 // ChannelRegistrationConfig controls channel registration.
 type ChannelRegistrationConfig struct {
-	Enabled bool
+	Enabled               bool
+	MaxChannelsPerAccount int `yaml:"max-channels-per-account"`
 }
 
 // OperClassConfig defines a specific operator class.
@@ -789,6 +790,10 @@ func LoadConfig(filename string) (config *Config, err error) {
 		config.Accounts.Registration.BcryptCost = passwd.DefaultCost
 	}
 
+	if config.Channels.Registration.MaxChannelsPerAccount == 0 {
+		config.Channels.Registration.MaxChannelsPerAccount = 10
+	}
+
 	// in the current implementation, we disable history by creating a history buffer
 	// with zero capacity. but the `enabled` config option MUST be respected regardless
 	// of this detail