add admin command

backend/app/User/EnvironmentInitialAdminCredentialsProvider.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace App\User;
+
+use RuntimeException;
+
+class EnvironmentInitialAdminCredentialsProvider implements
+    InitialAdminCredentialsProvider
+{
+    public function getCredentials(): InitialAdminCredentials
+    {
+        return new InitialAdminCredentials(
+            email: $this->requiredEnvironmentValue(
+                'RABBI_GERZI_INITIAL_ADMIN_EMAIL',
+            ),
+            password: $this->requiredEnvironmentValue(
+                'RABBI_GERZI_INITIAL_ADMIN_PASSWORD',
+            ),
+        );
+    }
+
+    private function requiredEnvironmentValue(string $key): string
+    {
+        $value = getenv($key);
+        if (! is_string($value) || trim($value) === '') {
+            throw new RuntimeException("$key is required");
+        }
+
+        return $value;
+    }
+}