Add Better Auth admin authentication

tests/better-auth-env.test.ts

@@ -0,0 +1,47 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import { getBetterAuthServerConfig } from "../convex/betterAuth/env";
+
+test("getBetterAuthServerConfig requires BETTER_AUTH_SECRET", () => {
+  assert.throws(
+    () => getBetterAuthServerConfig({}),
+    /Missing BETTER_AUTH_SECRET/,
+  );
+});
+
+test("getBetterAuthServerConfig can use a placeholder secret for schema generation", () => {
+  const config = getBetterAuthServerConfig(
+    {},
+    { allowMissingSecret: true },
+  );
+
+  assert.deepEqual(config, {
+    appUrl: "http://localhost:3000",
+    secret: "convex-better-auth-schema-generation-secret",
+  });
+});
+
+test("getBetterAuthServerConfig uses BETTER_AUTH_URL before NEXT_PUBLIC_APP_URL", () => {
+  const config = getBetterAuthServerConfig({
+    BETTER_AUTH_SECRET: "test-secret",
+    BETTER_AUTH_URL: "http://auth.local",
+    NEXT_PUBLIC_APP_URL: "http://app.local",
+  });
+
+  assert.deepEqual(config, {
+    appUrl: "http://auth.local",
+    secret: "test-secret",
+  });
+});
+
+test("getBetterAuthServerConfig falls back to local app URL", () => {
+  const config = getBetterAuthServerConfig({
+    BETTER_AUTH_SECRET: "test-secret",
+  });
+
+  assert.deepEqual(config, {
+    appUrl: "http://localhost:3000",
+    secret: "test-secret",
+  });
+});