Add api.fetchOptions to allow customising fetch() behaviour

This allows sending custom HTTP headers or including cookies in the
request!

docs/config.md

@@ -24,6 +24,7 @@ window.owntracks.config = {};
 
 - `api`
   - [`baseUrl`](#apibaseurl)
+  - [`fetchOptions`](#apifetchoptions)
 - [`endDateTime`](#enddatetime)
 - [`ignorePingLocation`](#ignorepinglocation)
 - [`locale`](#locale)
@@ -89,6 +90,26 @@ Base URL for the recorder's HTTP and WebSocket API. Keep CORS in mind.
   };
   ```
 
+### `api.fetchOptions`
+
+Options for API requests (made with `fetch()`). See [`fetch()` docs on MDN] for details.
+
+You can use this for example to send custom HTTP headers or to include cookies in the request.
+
+- Type: [`Object`]
+- Default: `{}`
+- Example:
+  ```js
+  // Include credentials (e.g. cookies)
+  window.owntracks.config = {
+    api: {
+      fetchOptions: {
+        credentials: "include"
+      }
+    }
+  };
+  ```
+
 ### `endDateTime`
 
 Initial end date and time (browser timezone) for fetched data.
@@ -458,3 +479,4 @@ Whether to enable verbose mode or not.
 [`object`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object
 [`string`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String
 [css `<color>`]: https://developer.mozilla.org/en-US/docs/Web/CSS/color_value
+[`fetch()` docs on MDN]: https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch#Parameters

src/api.js

@@ -1,3 +1,4 @@
+import config from "@/config";
 import { log, logLevels } from "@/logging";
 import { getApiUrl, getLocationHistoryCount } from "@/util";
 
@@ -12,7 +13,9 @@ const fetchApi = (path, params = {}) => {
   const url = getApiUrl(path);
   Object.keys(params).forEach(key => url.searchParams.append(key, params[key]));
   log("HTTP", `GET ${url.href}`);
-  return fetch(url.href).catch(error => log("HTTP", error, logLevels.ERROR));
+  return fetch(url.href, config.api.fetchOptions).catch(error =>
+    log("HTTP", error, logLevels.ERROR)
+  );
 };
 
 /**

src/config.js

@@ -10,6 +10,7 @@ startDateTime.setHours(0, 0, 0, 0);
 const DEFAULT_CONFIG = {
   api: {
     baseUrl: `${window.location.protocol}//${window.location.host}`,
+    fetchOptions: {},
   },
   endDateTime,
   ignorePingLocation: true,