feat(mcp): add REST-backed resource management tools (#12163)

app/Support/PostgresUser.php

@@ -0,0 +1,54 @@
+<?php
+
+namespace App\Support;
+
+/**
+ * Finds the PostgreSQL user inside a database container, the same way for backups and imports.
+ *
+ * The official image uses POSTGRES_USER (default "postgres"). Other images use PGUSER (read
+ * by libpq) or POSTGRESQL_USERNAME (Bitnami). When none is set, "postgres" is only a guess,
+ * so callers must check the connection before they change data.
+ */
+final class PostgresUser
+{
+    /**
+     * @var list<string>
+     */
+    public const ENV_NAMES = ['POSTGRES_USER', 'PGUSER', 'POSTGRESQL_USERNAME'];
+
+    public const DEFAULT = 'postgres';
+
+    /**
+     * Shell parameter expansion that resolves the user from the container environment.
+     */
+    public static function shellExpression(): string
+    {
+        return array_reduce(
+            array_reverse(self::ENV_NAMES),
+            fn (string $fallback, string $name): string => '${'.$name.':-'.$fallback.'}',
+            self::DEFAULT,
+        );
+    }
+
+    /**
+     * Resolves the user from `env` output lines (NAME=value) of the container.
+     *
+     * @param  iterable<string>  $envLines
+     */
+    public static function fromEnvLines(iterable $envLines): string
+    {
+        $values = [];
+        foreach ($envLines as $line) {
+            [$name, $value] = array_pad(explode('=', trim((string) $line), 2), 2, '');
+            $values[$name] = $value;
+        }
+
+        foreach (self::ENV_NAMES as $name) {
+            if (($values[$name] ?? '') !== '') {
+                return $values[$name];
+            }
+        }
+
+        return self::DEFAULT;
+    }
+}