External Chat Linking (!4)

This PR adds the functionality for plugins to send and recieve messages linked to a specific channel.

Co-authored-by: Layla <layla@layla.gg>
Reviewed-on: https://gitea.sumulayla.synology.me/layla/birdbot/pulls/4

app/external_chat_manager.go

@@ -0,0 +1,26 @@
+package app
+
+import (
+	"github.com/yeslayla/birdbot/common"
+	"github.com/yeslayla/birdbot/core"
+)
+
+type ExternalChatManager struct {
+	chat    common.ExternalChatModule
+	channel *core.Channel
+	bot     *Bot
+}
+
+func (manager *ExternalChatManager) SendMessage(user string, message string) {
+	manager.bot.Session.WebhookSendMessage(manager.channel, user, message)
+}
+
+func (app *Bot) InitalizeExternalChat(channel *core.Channel, chat common.ExternalChatModule) {
+	manager := &ExternalChatManager{
+		channel: channel,
+		chat:    chat,
+		bot:     app,
+	}
+
+	manager.chat.Initialize(manager)
+}