Complement GuildParams struct to comply with Discord's API (#1255)

* complement `GuildParams` struct [fix #994]

* fix: naming and spelling

* fix: gofmt

* refactor: use Locale type for PreferredLocale

Co-authored-by: zekro <private@zekro.de>
Co-authored-by: Fedor Lapshin <fe.lap.prog@gmail.com>

structs.go

@@ -1063,8 +1063,10 @@ type SystemChannelFlag int
 
 // Block containing known SystemChannelFlag values
 const (
-	SystemChannelFlagsSuppressJoin    SystemChannelFlag = 1 << 0
-	SystemChannelFlagsSuppressPremium SystemChannelFlag = 1 << 1
+	SystemChannelFlagsSuppressJoinNotifications         SystemChannelFlag = 1 << 0
+	SystemChannelFlagsSuppressPremium                   SystemChannelFlag = 1 << 1
+	SystemChannelFlagsSupressGuildReminderNotifications SystemChannelFlag = 1 << 2
+	SystemChannelFlagsSupressJoinNotificationReplies    SystemChannelFlag = 1 << 3
 )
 
 // IconURL returns a URL to the guild's icon.
@@ -1132,12 +1134,22 @@ type GuildParams struct {
 	Region                      string             `json:"region,omitempty"`
 	VerificationLevel           *VerificationLevel `json:"verification_level,omitempty"`
 	DefaultMessageNotifications int                `json:"default_message_notifications,omitempty"` // TODO: Separate type?
+	ExplicitContentFilter       int                `json:"explicit_content_filter,omitempty"`
 	AfkChannelID                string             `json:"afk_channel_id,omitempty"`
 	AfkTimeout                  int                `json:"afk_timeout,omitempty"`
 	Icon                        string             `json:"icon,omitempty"`
 	OwnerID                     string             `json:"owner_id,omitempty"`
 	Splash                      string             `json:"splash,omitempty"`
+	DiscoverySplash             string             `json:"discovery_splash,omitempty"`
 	Banner                      string             `json:"banner,omitempty"`
+	SystemChannelID             string             `json:"system_channel_id,omitempty"`
+	SystemChannelFlags          SystemChannelFlag  `json:"system_channel_flags,omitempty"`
+	RulesChannelID              string             `json:"rules_channel_id,omitempty"`
+	PublicUpdatesChannelID      string             `json:"public_updates_channel_id,omitempty"`
+	PreferredLocale             Locale             `json:"preferred_locale,omitempty"`
+	Features                    []GuildFeature     `json:"features,omitempty"`
+	Description                 string             `json:"description,omitempty"`
+	PremiumProgressBarEnabled   bool               `json:"premium_progress_bar_enabled,omitempty"`
 }
 
 // A Role stores information about Discord guild member roles.