Major refactoring and fixes.

* Split Node into multiple types and make sure fields are actually set
  when type says so.
* Refactor request handling.
* Start getting rid of moment as a dependency by using
  UnixTimestampSeconds instead.

server/utils/time.test.ts

@@ -0,0 +1,53 @@
+import {parseTimestamp} from "./time";
+import moment from "moment";
+
+const TIMESTAMP_INVALID_STRING = "2020-01-02T42:99:23.000Z";
+const TIMESTAMP_VALID_STRING = "2020-01-02T12:34:56.000Z";
+
+test('parseTimestamp() should fail parsing non-string timestamp', () => {
+    // given
+    const timestamp = {};
+
+    // when
+    const parsedTimestamp = parseTimestamp(timestamp);
+
+    // then
+    expect(parsedTimestamp).toEqual(null);
+});
+
+test('parseTimestamp() should fail parsing empty timestamp string', () => {
+    // given
+    const timestamp = "";
+
+    // when
+    const parsedTimestamp = parseTimestamp(timestamp);
+
+    // then
+    expect(parsedTimestamp).toEqual(null);
+});
+
+test('parseTimestamp() should fail parsing invalid timestamp string', () => {
+    // given
+    // noinspection UnnecessaryLocalVariableJS
+    const timestamp = TIMESTAMP_INVALID_STRING;
+
+    // when
+    const parsedTimestamp = parseTimestamp(timestamp);
+
+    // then
+    expect(parsedTimestamp).toEqual(null);
+});
+
+test('parseTimestamp() should succeed parsing valid timestamp string', () => {
+    // given
+    const timestamp = TIMESTAMP_VALID_STRING;
+
+    // when
+    const parsedTimestamp = parseTimestamp(timestamp);
+
+    // then
+    if (parsedTimestamp === null) {
+        fail('timestamp should not be null');
+    }
+    expect(moment.unix(parsedTimestamp).toISOString()).toEqual(timestamp);
+});