feat(cli_tools): Enable override of analytics API URL (#85)

Enable override of the analytics reporting API URL, and of the API call
timeout.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Analytics endpoint and request timeout are now configurable parameters
with sensible defaults.

* **Documentation**
* Clarified error handling documentation: only missing files return
null, while read/deserialize errors throw exceptions as expected.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: christerswahn

packages/cli_tools/lib/src/analytics/analytics.dart

@@ -15,18 +15,26 @@ abstract interface class Analytics {
 
 /// Analytics service for MixPanel.
 class MixPanelAnalytics implements Analytics {
+  static const _defaultEndpoint = 'https://api.mixpanel.com/track';
+  static const _defaultTimeout = Duration(seconds: 2);
+
   final String _uniqueUserId;
-  final String _endpoint = 'https://api.mixpanel.com/track';
+  final String _endpoint;
   final String _projectToken;
   final String _version;
+  final Duration _timeout;
 
   MixPanelAnalytics({
     required final String uniqueUserId,
     required final String projectToken,
     required final String version,
+    final String endpoint = _defaultEndpoint,
+    final Duration timeout = _defaultTimeout,
   })  : _uniqueUserId = uniqueUserId,
         _projectToken = projectToken,
-        _version = version;
+        _version = version,
+        _endpoint = endpoint,
+        _timeout = timeout;
 
   @override
   void cleanUp() {}
@@ -69,7 +77,7 @@ class MixPanelAnalytics implements Analytics {
           'Accept': 'text/plain',
           'Content-Type': 'application/x-www-form-urlencoded',
         },
-      ).timeout(const Duration(seconds: 2));
+      ).timeout(_timeout);
     } catch (e) {
       return;
     }

packages/cli_tools/lib/src/local_storage_manager/local_storage_manager.dart

@@ -84,8 +84,7 @@ abstract base class LocalStorageManager {
   }
 
   /// Tries to fetch and deserialize a json file from the local storage.
-  /// If the file does not exist or if an error occurs during reading or
-  /// deserialization, null will be returned.
+  /// If the file does not exist null will be returned.
   ///
   /// [fileName] The name of the file to fetch.
   /// [localStoragePath] The path to the local storage directory.