Ensured required config options cannot be left empty

module/Installer/src/Exception/ExceptionInterface.php

@@ -0,0 +1,10 @@
+<?php
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Installer\Exception;
+
+use Throwable;
+
+interface ExceptionInterface extends Throwable
+{
+}

module/Installer/src/Exception/MissingRequiredOptionException.php

@@ -0,0 +1,15 @@
+<?php
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Installer\Exception;
+
+use RuntimeException;
+use function sprintf;
+
+class MissingRequiredOptionException extends RuntimeException implements ExceptionInterface
+{
+    public static function fromOption(string $optionName): self
+    {
+        return new self(sprintf('The "%s" is required and can\'t be empty', $optionName));
+    }
+}