Created a config prost-processor which adds the base path on every applicable configuration

module/Core/src/Config/BasePathPrefixer.php

@@ -0,0 +1,39 @@
+<?php
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Core\Config;
+
+use function Functional\map;
+
+class BasePathPrefixer
+{
+    public function __invoke(array $config): array
+    {
+        $basePath = $config['router']['base_path'] ?? '';
+        $config['routes'] = $this->prefixRoutesWithBasePath($config, $basePath);
+        $config['middleware_pipeline'] = $this->prefixMiddlewarePathsWithBasePath($config, $basePath);
+        $config['url_shortener']['domain']['hostname'] .= $basePath;
+
+        return $config;
+    }
+
+    private function prefixRoutesWithBasePath(array $config, string $basePath): array
+    {
+        return map($config['routes'] ?? [], function (array $route) use ($basePath) {
+            $route['path'] = $basePath . $route['path'];
+            return $route;
+        });
+    }
+
+    private function prefixMiddlewarePathsWithBasePath(array $config, string $basePath): array
+    {
+        return map($config['middleware_pipeline'] ?? [], function (array $middleware) use ($basePath) {
+            if (! isset($middleware['path'])) {
+                return $middleware;
+            }
+
+            $middleware['path'] = $basePath . $middleware['path'];
+            return $middleware;
+        });
+    }
+}

module/Core/src/Config/SimplifiedConfigParser.php

@@ -0,0 +1,62 @@
+<?php
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Core\Config;
+
+use Shlinkio\Shlink\Installer\Util\PathCollection;
+use Zend\Stdlib\ArrayUtils;
+
+use function array_intersect_key;
+use function array_key_exists;
+use function Functional\contains;
+use function Functional\reduce_left;
+
+class SimplifiedConfigParser
+{
+    private const SIMPLIFIED_CONFIG_MAPPING = [
+        'disable_track_param' => ['app_options', 'disable_track_param'],
+        'short_domain_schema' => ['url_shortener', 'domain', 'schema'],
+        'short_domain_host' => ['url_shortener', 'domain', 'hostname'],
+        'validate_url' => ['url_shortener', 'validate_url'],
+        'not_found_redirect_to' => ['url_shortener', 'not_found_short_url', 'redirect_to'],
+        'db_config' => ['entity_manager', 'connection'],
+        'delete_short_url_threshold' => ['delete_short_urls', 'visits_threshold'],
+        'redis_servers' => ['redis', 'servers'],
+        'base_path' => ['router', 'base_path'],
+    ];
+    private const SIMPLIFIED_CONFIG_SIDE_EFFECTS = [
+        'not_found_redirect_to' => [
+            'path' => ['url_shortener', 'not_found_short_url', 'enable_redirection'],
+            'value' => true,
+        ],
+        'delete_short_url_threshold' => [
+            'path' => ['delete_short_urls', 'check_visits_threshold'],
+            'value' => true,
+        ],
+        'redis_servers' => [
+            'path' => ['dependencies', 'aliases', 'lock_store'],
+            'value' => 'redis_lock_store',
+        ],
+    ];
+    private const SIMPLIFIED_MERGEABLE_CONFIG = ['db_config'];
+
+    public function __invoke(array $config): array
+    {
+        $existingKeys = array_intersect_key($config, self::SIMPLIFIED_CONFIG_MAPPING);
+
+        return reduce_left($existingKeys, function ($value, string $key, $c, PathCollection $collection) {
+            $path = self::SIMPLIFIED_CONFIG_MAPPING[$key];
+            if (contains(self::SIMPLIFIED_MERGEABLE_CONFIG, $key)) {
+                $value = ArrayUtils::merge($collection->getValueInPath($path), $value);
+            }
+
+            $collection->setValueInPath($value, $path);
+            if (array_key_exists($key, self::SIMPLIFIED_CONFIG_SIDE_EFFECTS)) {
+                ['path' => $sideEffectPath, 'value' => $sideEffectValue] = self::SIMPLIFIED_CONFIG_SIDE_EFFECTS[$key];
+                $collection->setValueInPath($sideEffectValue, $sideEffectPath);
+            }
+
+            return $collection;
+        }, new PathCollection($config))->toArray();
+    }
+}