feat: allow env variables to overwrite smtp config

Fixes #3

src/common.ts

@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2019 StApps
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+ /**
+  * A recursive partial object
+  *
+  * Copied from https://stackoverflow.com/a/51365037
+  */
+export type RecursivePartial<T> = {
+  [P in keyof T]?: T[P] extends Array<infer U> ?
+  Array<RecursivePartial<U>> :
+  T[P] extends object ? RecursivePartial<T[P]> : T[P];
+};
+
+/**
+ * Deletes all properties that are undefined from an object
+ * @param obj
+ */
+export function deleteUndefinedProperties(obj: any) {
+  // return atomic data types and arrays (recursion anchor)
+  if (typeof obj !== 'object' || Array.isArray(obj)) {
+    return obj;
+  }
+
+  // check each key
+  Object.keys(obj).forEach((key) => {
+    if (typeof obj[key] === 'undefined') {
+      // delete undefined keys
+      delete obj[key];
+    } else {
+      // check recursive
+      obj[key] = deleteUndefinedProperties(obj[key]);
+    }
+  });
+
+  return obj;
+}