feat(supabase_flutter): Make Supabase.initialize() idempotent (#1194)

[Supabase] Make initialize() idempotent

This PR introduces a minor update to the initialize() method to avoid throwing when called multiple times. Instead, it logs an informational message and returns the existing instance, making initialization idempotent and smoother for production use.

- Replaced assert(!_instance.isInitialized) with a runtime check to prevent throwing.
- Added _log.info() when a reinitialization attempt occurs.
- Exposed isInitialized as a public read-only getter for improved observability.
- Avoids throwing errors in release mode by gracefully handling repeated initialization.

Author: iosephmagno

packages/supabase_flutter/lib/src/supabase.dart

@@ -42,7 +42,7 @@ class Supabase with WidgetsBindingObserver {
   /// Call [Supabase.initialize] to initialize it.
   static Supabase get instance {
     assert(
-      _instance._initialized,
+      _instance._isInitialized,
       'You must initialize the supabase instance before calling Supabase.instance',
     );
     return _instance;
@@ -87,10 +87,11 @@ class Supabase with WidgetsBindingObserver {
     Future<String?> Function()? accessToken,
     bool? debug,
   }) async {
-    assert(
-      !_instance._initialized,
-      'This instance is already initialized',
-    );
+    if (_instance._isInitialized) {
+      _log.info('Supabase is already initialized. Skipping reinitialization.');
+      return _instance;
+    }
+
     _instance._debugEnable = debug ?? kDebugMode;
 
     if (_instance._debugEnable) {
@@ -152,7 +153,10 @@ class Supabase with WidgetsBindingObserver {
 
   static WidgetsBinding? get _widgetsBindingInstance => WidgetsBinding.instance;
 
-  bool _initialized = false;
+  bool _isInitialized = false;
+
+  /// Whether the Supabase instance has been initialized. Useful for debugging.
+  bool get isInitialized => _isInitialized;
 
   /// The supabase client for this instance
   ///
@@ -177,7 +181,7 @@ class Supabase with WidgetsBindingObserver {
     client.dispose();
     _instance._supabaseAuth?.dispose();
     _widgetsBindingInstance?.removeObserver(this);
-    _initialized = false;
+    _isInitialized = false;
   }
 
   void _init(
@@ -214,7 +218,7 @@ class Supabase with WidgetsBindingObserver {
       markClientToDispose(client);
     }
     _widgetsBindingInstance?.addObserver(this);
-    _initialized = true;
+    _isInitialized = true;
   }
 
   @override