feat: MCP plugin (#2666)

* chore: wip

* wip

* feat: mcp plugin

* wip

* chore: fix lock file

* clean up

* schema

* docs

* chore: lint

* chore: release v1.2.9-beta.1

* blog

* chore: lint

examples/nextjs-mcp/lib/auth.ts

@@ -0,0 +1,16 @@
+import { betterAuth } from "better-auth";
+import { mcp } from "better-auth/plugins";
+import Database from "better-sqlite3";
+
+export const auth = betterAuth({
+	database: new Database("./auth.db"),
+	baseURL: "http://localhost:3000",
+	plugins: [
+		mcp({
+			loginPage: "/login",
+		}),
+	],
+	emailAndPassword: {
+		enabled: true,
+	},
+});