fix: use useradd instead of adduser for cross-version compatibility (#1182)

Replace adduser with useradd for mongodb_exporter user creation.
The --comment option in adduser is not supported in Debian 11,
only in Debian 12+. useradd works consistently across all versions.

Co-authored-by: Jiří Čtvrtka <[email protected]>

Author: izmal

.scripts/postinst

@@ -4,7 +4,11 @@ set -e
 
 echo "Creating user and group..."
 
-adduser --system --no-create-home --comment "Mongodb Exporter User" mongodb_exporter
+useradd --system \
+        --no-create-home \
+        --shell /sbin/nologin \
+        --comment "MongoDB Exporter" \
+        mongodb_exporter
 
 systemctl daemon-reload > dev/null || exit $?