feat: Add dockerSecret.ts to replace docker-secret

Replace the unnecessary dependency.

src/util/dockerSecret.ts

@@ -0,0 +1,40 @@
+/**
+ * Modified from
+ * https://github.com/hwkd/docker-secret/tree/6fa920ac16d383b173db33ed04554754cf418aed
+ * on 2023-11-28
+ * under MIT license
+ * https://github.com/hwkd/docker-secret/blob/6fa920ac16d383b173db33ed04554754cf418aed/LICENSE
+ *
+ * The purpose of copying this small module here is to reduce the attack surface
+ * regarding supply chain attacks.
+ */
+import fs from "node:fs";
+import path from "node:path";
+
+// Default secrets directory.
+const SECRET_DIR = "/run/secrets";
+
+// Keep the type here instead of in types.ts to keep this module self-contained
+// and a straightforward copy of the original.
+export type Secrets = Record<string, string>;
+
+export const getSecrets = <T extends Secrets = Secrets>(
+  secretDir?: string,
+): T => {
+  const dir = secretDir ?? SECRET_DIR;
+
+  const secrets: Secrets = {};
+  if (fs.existsSync(dir)) {
+    fs.readdirSync(dir).forEach((file) => {
+      const fullPath = path.join(dir, file);
+
+      if (fs.lstatSync(fullPath).isDirectory()) {
+        return;
+      }
+
+      secrets[file] = fs.readFileSync(fullPath, "utf8").trim();
+    });
+  }
+
+  return secrets as T;
+};