Migrate WelcomeMessage to new Plugin structure

backend/src/plugins/WelcomeMessage/WelcomeMessagePlugin.ts

@@ -0,0 +1,29 @@
+import { zeppelinPlugin } from "../ZeppelinPluginBlueprint";
+import { PluginOptions } from "knub";
+import { WelcomeMessagePluginType, ConfigSchema } from "./types";
+import { GuildLogs } from "src/data/GuildLogs";
+import { GuildMemberAddEvt } from "./events/GuildMemberAddEvt";
+
+const defaultOptions: PluginOptions<WelcomeMessagePluginType> = {
+  config: {
+    send_dm: false,
+    send_to_channel: null,
+    message: "",
+  },
+};
+
+export const WelcomeMessagePlugin = zeppelinPlugin<WelcomeMessagePluginType>()("welcome_message", {
+  configSchema: ConfigSchema,
+  defaultOptions,
+
+  // prettier-ignore
+  events: [
+    GuildMemberAddEvt,
+  ],
+
+  onLoad(pluginData) {
+    const { state, guild } = pluginData;
+
+    state.logs = new GuildLogs(guild.id);
+  },
+});