Add proposal approval api endpoint

Change-Id: I3ab864af51735ee7c484df9c66d0b3ec2f6acb36
diff --git a/server/config.yaml b/server/config.yaml
index 0842f0e..5ce3fec 100644
--- a/server/config.yaml
+++ b/server/config.yaml
@@ -13,6 +13,7 @@
   token: "${GITHUB_TOKEN}"
   owner: "iomodo"  # Replace with your GitHub username
   repo: "staff"   # Replace with your repository name
+  webhook_secret: "${GITHUB_WEBHOOK_SECRET}"  # Secret for webhook signature validation
 
 git:
   repo_path: "/Users/shota/github/staff/"