chore: Only support installer 3.4 and newer

Author: ralflang

.horde.yml

@@ -27,8 +27,10 @@ dependencies:
   required:
     php: ^8.1
     composer:
-      horde/horde-installer-plugin: ^3
+      horde/horde-installer-plugin: ^3.4
       horde/horde: ^6
       horde/routes: ^3
       hordectl: ^1
 vendor: horde
+keywords:
+  - root_component

composer.json

@@ -4,7 +4,7 @@
     "type": "project",
     "require": {
         "composer-plugin-api": "^2.2",
-        "horde/horde-installer-plugin": "^3 || dev-FRAMEWORK_6_0",
+        "horde/horde-installer-plugin": "^3.4 || dev-FRAMEWORK_6_0",
         "horde/horde": "^6 || dev-FRAMEWORK_6_0",
         "horde/routes": "^3 || dev-FRAMEWORK_6_0",
         "horde/hordectl": "^1 || dev-FRAMEWORK_6_0"