Add proposal approval api endpoint

Change-Id: I3ab864af51735ee7c484df9c66d0b3ec2f6acb36
diff --git a/server/config/config.go b/server/config/config.go
index 1a39c6f..2a39741 100644
--- a/server/config/config.go
+++ b/server/config/config.go
@@ -34,9 +34,10 @@
 
 // GitHubConfig represents GitHub integration configuration
 type GitHubConfig struct {
-	Token string `yaml:"token"`
-	Owner string `yaml:"owner"`
-	Repo  string `yaml:"repo"`
+	Token         string `yaml:"token"`
+	Owner         string `yaml:"owner"`
+	Repo          string `yaml:"repo"`
+	WebhookSecret string `yaml:"webhook_secret"` // Secret for webhook signature validation
 }
 
 // GerritConfig represents Gerrit integration configuration
@@ -118,6 +119,9 @@
 	if repo := os.Getenv("GITHUB_REPO"); repo != "" {
 		config.GitHub.Repo = repo
 	}
+	if webhookSecret := os.Getenv("GITHUB_WEBHOOK_SECRET"); webhookSecret != "" {
+		config.GitHub.WebhookSecret = webhookSecret
+	}
 	if gerritUsername := os.Getenv("GERRIT_USERNAME"); gerritUsername != "" {
 		config.Gerrit.Username = gerritUsername
 	}