[5.8] Make register method in the ServiceProvider as part of the contract

 In the laravel#27067 pr was added DeferrableProvider service provider.
 This Pr will add pretty the same thing.
 In case, if it will be accepted then I will add documentation for this.

----------------

Also i thing will be good to add diferent contract for the:
- method `boot`
- property `singletons` and `bindings`

Author: TBlindaruk

src/Illuminate/Auth/AuthServiceProvider.php

@@ -4,10 +4,11 @@
 
 use Illuminate\Auth\Access\Gate;
 use Illuminate\Support\ServiceProvider;
+use Illuminate\Contracts\Support\RegistrableProvider;
 use Illuminate\Contracts\Auth\Access\Gate as GateContract;
 use Illuminate\Contracts\Auth\Authenticatable as AuthenticatableContract;
 
-class AuthServiceProvider extends ServiceProvider
+class AuthServiceProvider extends ServiceProvider implements RegistrableProvider
 {
     /**
      * Register the service provider.

src/Illuminate/Auth/Passwords/PasswordResetServiceProvider.php

@@ -4,8 +4,9 @@
 
 use Illuminate\Support\ServiceProvider;
 use Illuminate\Contracts\Support\DeferrableProvider;
+use Illuminate\Contracts\Support\RegistrableProvider;
 
-class PasswordResetServiceProvider extends ServiceProvider implements DeferrableProvider
+class PasswordResetServiceProvider extends ServiceProvider implements DeferrableProvider, RegistrableProvider
 {
     /**
      * Register the service provider.

src/Illuminate/Broadcasting/BroadcastServiceProvider.php

@@ -4,10 +4,11 @@
 
 use Illuminate\Support\ServiceProvider;
 use Illuminate\Contracts\Support\DeferrableProvider;
+use Illuminate\Contracts\Support\RegistrableProvider;
 use Illuminate\Contracts\Broadcasting\Factory as BroadcastingFactory;
 use Illuminate\Contracts\Broadcasting\Broadcaster as BroadcasterContract;
 
-class BroadcastServiceProvider extends ServiceProvider implements DeferrableProvider
+class BroadcastServiceProvider extends ServiceProvider implements DeferrableProvider, RegistrableProvider
 {
     /**
      * Register the service provider.

src/Illuminate/Bus/BusServiceProvider.php

@@ -4,11 +4,12 @@
 
 use Illuminate\Support\ServiceProvider;
 use Illuminate\Contracts\Support\DeferrableProvider;
+use Illuminate\Contracts\Support\RegistrableProvider;
 use Illuminate\Contracts\Bus\Dispatcher as DispatcherContract;
 use Illuminate\Contracts\Queue\Factory as QueueFactoryContract;
 use Illuminate\Contracts\Bus\QueueingDispatcher as QueueingDispatcherContract;
 
-class BusServiceProvider extends ServiceProvider implements DeferrableProvider
+class BusServiceProvider extends ServiceProvider implements DeferrableProvider, RegistrableProvider
 {
     /**
      * Register the service provider.

src/Illuminate/Cache/CacheServiceProvider.php

@@ -4,8 +4,9 @@
 
 use Illuminate\Support\ServiceProvider;
 use Illuminate\Contracts\Support\DeferrableProvider;
+use Illuminate\Contracts\Support\RegistrableProvider;
 
-class CacheServiceProvider extends ServiceProvider implements DeferrableProvider
+class CacheServiceProvider extends ServiceProvider implements DeferrableProvider, RegistrableProvider
 {
     /**
      * Register the service provider.

src/Illuminate/Contracts/Support/RegistrableProvider.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace Illuminate\Contracts\Support;
+
+interface RegistrableProvider
+{
+    /**
+     * Register the services.
+     *
+     * @return void
+     */
+    public function register();
+}

src/Illuminate/Cookie/CookieServiceProvider.php

@@ -3,8 +3,9 @@
 namespace Illuminate\Cookie;
 
 use Illuminate\Support\ServiceProvider;
+use Illuminate\Contracts\Support\RegistrableProvider;
 
-class CookieServiceProvider extends ServiceProvider
+class CookieServiceProvider extends ServiceProvider implements RegistrableProvider
 {
     /**
      * Register the service provider.

src/Illuminate/Database/DatabaseServiceProvider.php

@@ -7,11 +7,12 @@
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Support\ServiceProvider;
 use Illuminate\Contracts\Queue\EntityResolver;
+use Illuminate\Contracts\Support\RegistrableProvider;
 use Illuminate\Database\Connectors\ConnectionFactory;
 use Illuminate\Database\Eloquent\QueueEntityResolver;
 use Illuminate\Database\Eloquent\Factory as EloquentFactory;
 
-class DatabaseServiceProvider extends ServiceProvider
+class DatabaseServiceProvider extends ServiceProvider implements RegistrableProvider
 {
     /**
      * Bootstrap the application events.

src/Illuminate/Database/MigrationServiceProvider.php

@@ -6,9 +6,10 @@
 use Illuminate\Database\Migrations\Migrator;
 use Illuminate\Contracts\Support\DeferrableProvider;
 use Illuminate\Database\Migrations\MigrationCreator;
+use Illuminate\Contracts\Support\RegistrableProvider;
 use Illuminate\Database\Migrations\DatabaseMigrationRepository;
 
-class MigrationServiceProvider extends ServiceProvider implements DeferrableProvider
+class MigrationServiceProvider extends ServiceProvider implements DeferrableProvider, RegistrableProvider
 {
     /**
      * Register the service provider.

src/Illuminate/Encryption/EncryptionServiceProvider.php

@@ -5,8 +5,9 @@
 use RuntimeException;
 use Illuminate\Support\Str;
 use Illuminate\Support\ServiceProvider;
+use Illuminate\Contracts\Support\RegistrableProvider;
 
-class EncryptionServiceProvider extends ServiceProvider
+class EncryptionServiceProvider extends ServiceProvider implements RegistrableProvider
 {
     /**
      * Register the service provider.