Rework the implementation

[bdlukaa]

What kind of change does this PR introduce?

Rework the singleton

What is the current behavior?

To initialize it:

import 'package:supabase_flutter/supabase_flutter.dart';

void main() {
  WidgetsFlutterBinding.ensureInitialized();

  Supabase(
    url: SUPABASE_URL,
    anonKey: SUPABASE_ANNON_KEY,
    authCallbackUrlHostname: 'login-callback', // optional
    debug: true // optional
  );

  runApp(MyApp());
}

To access the supabase instance:

import 'package:supabase_flutter/supabase_flutter.dart';

final response = await Supabase().client.auth.signIn(email: _email, password: _password);

What is the new behavior?

To initialize it:

import 'package:supabase_flutter/supabase_flutter.dart';

void main() {
  WidgetsFlutterBinding.ensureInitialized();

  Supabase.initialize(
    url: SUPABASE_URL,
    anonKey: SUPABASE_ANNON_KEY,
    authCallbackUrlHostname: 'login-callback', // optional
    debug: true // optional
  );

  runApp(MyApp());
}

To access the supabase instance:

import 'package:supabase_flutter/supabase_flutter.dart';

final response = await Supabase.instance.client.auth.signIn(email: _email, password: _password);

Additional context

This rework comes with the purpose of making the library more dev-friendly. The documentation of some methods were also updated

[phamhieu]

Wow, that's fast. Great work! @bdlukaa. Thank you

Can you fix the 2 lint errors. I will merge the PR after that.

[bdlukaa]

@phamhieu done! Please test it before merging

[phamhieu]

@bdlukaa can you fix the unit test

[bdlukaa]

@phamhieu Done! All tests passing locally for me

✓ can access Supabase singleton
✓ can parse deeplink
✓ can parse flutter web redirect link
✓ can parse flutter web custom page redirect link