Migrate preview.url field in config

When the config has been created by a previous version, the preview.url
field may contain values wrapped in `url("...")`. The updated version no
longer requires this wrapper. If the preview.url field starts with `url(`
and ends with `)`, the `url(...)` wrapper and any surrounding quotes are
removed.

Signed-off-by: Nils Bosbach <n.bosbach@gmx.de>

Author: nbosb

src/Service/ConfigurationService.php

@@ -161,6 +161,11 @@ protected function processMigration(array $config): array
             $config['preview']['mode'] = 'device_cam';
         }
 
+        // Migrate Preview URL
+        if (isset($config['preview']['url']) && substr($config['preview']['url'], 0, 4) === 'url(' && substr($config['preview']['url'], -1) === ')') {
+            $config['preview']['url'] = trim(substr($config['preview']['url'], 4, -1), '"\'');
+        }
+
         return $config;
     }