Add support for postgres schema (#237)

* Add support for postgres schema

* wip

* Apply fixes from StyleCI

* revert to db as default for pgsql

* Move separate_by to database

* Fixing testing

* Fixing style

* Reverted change

* Store string instead of Connection instance

* Remove use statement

* Add use statement for DB facade

* mysql -> pgsql

Co-authored-by: Samuel Štancl <samuel.stancl@gmail.com>

src/TenantDatabaseManagers/PostgreSQLSchemaManager.php

@@ -0,0 +1,47 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Stancl\Tenancy\TenantDatabaseManagers;
+
+use Illuminate\Contracts\Config\Repository;
+use Illuminate\Database\Connection;
+use Illuminate\Support\Facades\DB;
+use Stancl\Tenancy\Contracts\Future\CanSetConnection;
+use Stancl\Tenancy\Contracts\TenantDatabaseManager;
+
+class PostgreSQLSchemaManager implements TenantDatabaseManager, CanSetConnection
+{
+    /** @var string */
+    protected $connection;
+
+    public function __construct(Repository $config)
+    {
+        $this->connection = $config->get('tenancy.database_manager_connections.pgsql');
+    }
+
+    protected function database(): Connection
+    {
+        return DB::connection($this->connection);
+    }
+
+    public function setConnection(string $connection): void
+    {
+        $this->connection = $connection;
+    }
+
+    public function createDatabase(string $name): bool
+    {
+        return $this->database()->statement("CREATE SCHEMA \"$name\"");
+    }
+
+    public function deleteDatabase(string $name): bool
+    {
+        return $this->database()->statement("DROP SCHEMA \"$name\"");
+    }
+
+    public function databaseExists(string $name): bool
+    {
+        return (bool) $this->database()->select("SELECT schema_name FROM information_schema.schemata WHERE schema_name = '$name'");
+    }
+}