feat: enable user registration control via environment variable in Gitea configuration

Signed-off-by: zhenyus <zhenyus@mathmast.com>

freeleaps/helm-pkg/3rd/gitea/values.prod.yaml

@@ -530,8 +530,6 @@ gitea:
     server:
       SSH_PORT: 22 # rootful image
       SSH_LISTEN_PORT: 2222 # rootless image
-    service:
-      DISABLE_REGISTRATION: "true"
   #
   #  security:
   #    PASSWORD_COMPLEXITY: spec
@@ -544,7 +542,9 @@ gitea:
   #       name: gitea-app-ini-plaintext
 
   ## @param gitea.additionalConfigFromEnvs Additional configuration sources from environment variables
-  additionalConfigFromEnvs: []
+  additionalConfigFromEnvs: 
+    - name: DISABLE_REGISTRATION
+      value: "true"
 
   ## @param gitea.podAnnotations Annotations for the Gitea pod
   podAnnotations: {}