Refactor formatTime into util class (#3073)

While looking at https://github.com/MichMich/MagicMirror/pull/3070 I
noticed that the weather and clock module do some formatTime stuff, so
why not use a common function for that?

---------

Co-authored-by: veeck <michael@veeck.de>

tests/unit/modules/default/utils_spec.js

@@ -1,8 +1,9 @@
-const { performWebRequest } = require("../../../../modules/default/utils");
+global.moment = require("moment-timezone");
+const { performWebRequest, formatTime } = require("../../../../modules/default/utils");
 
 const nodeVersion = process.version.match(/^v(\d+)\.*/)[1];
 
-describe("Utils tests", () => {
+describe("Default modules utils tests", () => {
 	describe("The performWebRequest-method", () => {
 		if (nodeVersion > 18) {
 			const locationHost = "localhost:8080";
@@ -109,4 +110,78 @@ describe("Utils tests", () => {
 			test("Always ok, need one test", () => {});
 		}
 	});
+
+	describe("formatTime", () => {
+		const time = new Date();
+
+		beforeAll(() => {
+			jest.useFakeTimers();
+			moment.tz.setDefault("Europe/Berlin");
+		});
+
+		beforeEach(async () => {
+			jest.setSystemTime(new Date("2023-01-01 13:13"));
+		});
+
+		afterEach(async () => {
+			jest.setSystemTime(new Date());
+		});
+
+		afterAll(() => {
+			jest.useRealTimers();
+		});
+
+		it("should convert correctly according to the config", () => {
+			time.setHours(13, 13);
+			expect(
+				formatTime(
+					{
+						timeFormat: 24
+					},
+					time
+				)
+			).toBe("13:13");
+			expect(
+				formatTime(
+					{
+						showPeriod: true,
+						showPeriodUpper: true,
+						timeFormat: 12
+					},
+					time
+				)
+			).toBe("1:13 PM");
+			expect(
+				formatTime(
+					{
+						showPeriod: true,
+						showPeriodUpper: false,
+						timeFormat: 12
+					},
+					time
+				)
+			).toBe("1:13 pm");
+			expect(
+				formatTime(
+					{
+						showPeriod: false,
+						timeFormat: 12
+					},
+					time
+				)
+			).toBe("1:13");
+		});
+
+		it("should convert correctly into another timezone", () => {
+			expect(
+				formatTime(
+					{
+						timeFormat: 24,
+						timezone: "America/Toronto"
+					},
+					time
+				)
+			).toBe("07:13");
+		});
+	});
 });