feat: add configurable logging level for backend and Mini App

- Introduced a new `LOG_LEVEL` configuration option in the `.env.example` file to allow users to set the logging level (DEBUG, INFO, WARNING, ERROR).
- Updated the `Settings` class to include the `log_level` attribute, normalizing its value to ensure valid logging levels are used.
- Modified the logging setup in `run.py` to utilize the configured log level, enhancing flexibility in log management.
- Enhanced the Mini App to include the logging level in the JavaScript configuration, allowing for consistent logging behavior across the application.
- Added a new `logger.js` module for frontend logging, implementing level-based filtering and console delegation.
- Included unit tests for the new logger functionality to ensure proper behavior and level handling.

webapp/js/logger.test.js

@@ -0,0 +1,94 @@
+/**
+ * Unit tests for logger: level filtering and console delegation.
+ */
+
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { logger } from "./logger.js";
+
+describe("logger", () => {
+  const origWindow = globalThis.window;
+
+  beforeEach(() => {
+    vi.spyOn(console, "debug").mockImplementation(() => {});
+    vi.spyOn(console, "info").mockImplementation(() => {});
+    vi.spyOn(console, "warn").mockImplementation(() => {});
+    vi.spyOn(console, "error").mockImplementation(() => {});
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+    if (globalThis.window) {
+      delete globalThis.window.__DT_LOG_LEVEL;
+    }
+  });
+
+  function setLevel(level) {
+    if (!globalThis.window) globalThis.window = {};
+    globalThis.window.__DT_LOG_LEVEL = level;
+  }
+
+  it("at level info does not call console.debug", () => {
+    setLevel("info");
+    logger.debug("test");
+    expect(console.debug).not.toHaveBeenCalled();
+  });
+
+  it("at level info calls console.info for logger.info", () => {
+    setLevel("info");
+    logger.info("hello");
+    expect(console.info).toHaveBeenCalledWith("[DutyTeller][info]", "hello");
+  });
+
+  it("at level info calls console.warn and console.error", () => {
+    setLevel("info");
+    logger.warn("w");
+    logger.error("e");
+    expect(console.warn).toHaveBeenCalledWith("[DutyTeller][warn]", "w");
+    expect(console.error).toHaveBeenCalledWith("[DutyTeller][error]", "e");
+  });
+
+  it("at level debug calls console.debug", () => {
+    setLevel("debug");
+    logger.debug("dbg");
+    expect(console.debug).toHaveBeenCalledWith("[DutyTeller][debug]", "dbg");
+  });
+
+  it("at level error does not call console.debug or console.info", () => {
+    setLevel("error");
+    logger.debug("d");
+    logger.info("i");
+    expect(console.debug).not.toHaveBeenCalled();
+    expect(console.info).not.toHaveBeenCalled();
+  });
+
+  it("at level error calls console.error", () => {
+    setLevel("error");
+    logger.error("err");
+    expect(console.error).toHaveBeenCalledWith("[DutyTeller][error]", "err");
+  });
+
+  it("passes extra args to console", () => {
+    setLevel("info");
+    logger.info("msg", { foo: 1 }, "bar");
+    expect(console.info).toHaveBeenCalledWith(
+      "[DutyTeller][info]",
+      "msg",
+      { foo: 1 },
+      "bar"
+    );
+  });
+
+  it("defaults to info when __DT_LOG_LEVEL is missing", () => {
+    if (globalThis.window) delete globalThis.window.__DT_LOG_LEVEL;
+    logger.debug("no");
+    expect(console.debug).not.toHaveBeenCalled();
+    logger.info("yes");
+    expect(console.info).toHaveBeenCalledWith("[DutyTeller][info]", "yes");
+  });
+
+  it("defaults to info when __DT_LOG_LEVEL is invalid", () => {
+    setLevel("invalid");
+    logger.debug("no");
+    expect(console.debug).not.toHaveBeenCalled();
+  });
+});