Postgres RLS + permission controlled database managers (#33)

This PR adds Postgres RLS (trait manager + table manager approach) and permission controlled managers for PostgreSQL.

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Co-authored-by: lukinovec <lukinovec@gmail.com>
Co-authored-by: PHP CS Fixer <phpcsfixer@example.com>

src/Database/Exceptions/RecursiveRelationshipException.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Stancl\Tenancy\Database\Exceptions;
+
+use Exception;
+
+/**
+ * @see \Stancl\Tenancy\RLS\PolicyManagers\TableRLSManager
+ */
+class RecursiveRelationshipException extends Exception
+{
+    public function __construct(string|null $message = null)
+    {
+        parent::__construct($message ?? "Table's foreign key referenced multiple times in the same path.");
+    }
+}

src/Database/Exceptions/TableNotRelatedToTenantException.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Stancl\Tenancy\Database\Exceptions;
+
+use Exception;
+
+/**
+ * @see \Stancl\Tenancy\RLS\PolicyManagers\TraitRLSManager
+ */
+class TableNotRelatedToTenantException extends Exception
+{
+    public function __construct(string $table)
+    {
+        parent::__construct("Table $table does not belong to a tenant directly or through another table.");
+    }
+}