refactor: improve language normalization and date handling utilities

- Introduced a new `normalize_lang` function to standardize language codes across the application, ensuring consistent handling of user language preferences.
- Refactored date handling utilities by adding `parse_utc_iso` and `parse_utc_iso_naive` functions for better parsing of ISO 8601 date strings, enhancing timezone awareness.
- Updated various modules to utilize the new language normalization and date parsing functions, improving code clarity and maintainability.
- Enhanced error handling in date validation to raise specific `DateRangeValidationError` exceptions, providing clearer feedback on validation issues.
- Improved test coverage for date range validation and language normalization functionalities, ensuring robustness and reliability.

webapp/js/api.js

@@ -21,6 +21,27 @@ export function buildFetchOptions(initData) {
   return { headers, signal: controller.signal, timeoutId };
 }
 
+/**
+ * GET request to API with init data, Accept-Language, timeout.
+ * Caller checks res.ok, res.status, res.json().
+ * @param {string} path - e.g. "/api/duties"
+ * @param {{ from?: string, to?: string }} params - query params
+ * @returns {Promise<Response>} - raw response
+ */
+export async function apiGet(path, params = {}) {
+  const base = window.location.origin;
+  const query = new URLSearchParams(params).toString();
+  const url = query ? `${base}${path}?${query}` : `${base}${path}`;
+  const initData = getInitData();
+  const opts = buildFetchOptions(initData);
+  try {
+    const res = await fetch(url, { headers: opts.headers, signal: opts.signal });
+    return res;
+  } finally {
+    clearTimeout(opts.timeoutId);
+  }
+}
+
 /**
  * Fetch duties for date range. Throws ACCESS_DENIED error on 403.
  * @param {string} from - YYYY-MM-DD
@@ -28,17 +49,8 @@ export function buildFetchOptions(initData) {
  * @returns {Promise<object[]>}
  */
 export async function fetchDuties(from, to) {
-  const base = window.location.origin;
-  const url =
-    base +
-    "/api/duties?from=" +
-    encodeURIComponent(from) +
-    "&to=" +
-    encodeURIComponent(to);
-  const initData = getInitData();
-  const opts = buildFetchOptions(initData);
   try {
-    const res = await fetch(url, { headers: opts.headers, signal: opts.signal });
+    const res = await apiGet("/api/duties", { from, to });
     if (res.status === 403) {
       let detail = t(state.lang, "access_denied");
       try {
@@ -63,8 +75,6 @@ export async function fetchDuties(from, to) {
       throw new Error(t(state.lang, "error_network"));
     }
     throw e;
-  } finally {
-    clearTimeout(opts.timeoutId);
   }
 }
 
@@ -75,22 +85,11 @@ export async function fetchDuties(from, to) {
  * @returns {Promise<object[]>}
  */
 export async function fetchCalendarEvents(from, to) {
-  const base = window.location.origin;
-  const url =
-    base +
-    "/api/calendar-events?from=" +
-    encodeURIComponent(from) +
-    "&to=" +
-    encodeURIComponent(to);
-  const initData = getInitData();
-  const opts = buildFetchOptions(initData);
   try {
-    const res = await fetch(url, { headers: opts.headers, signal: opts.signal });
+    const res = await apiGet("/api/calendar-events", { from, to });
     if (!res.ok) return [];
     return res.json();
   } catch (e) {
     return [];
-  } finally {
-    clearTimeout(opts.timeoutId);
   }
 }