Add stages definition including Prosper and custom stages

.gitlab-ci.yml

@@ -7,6 +7,14 @@ variables:
 # renovate: datasource=gitlab-tags depName=esv/bsf/pypi/prosper versioning=semver registryUrl=https://gitlab.global.bsf.tools
   PROSPER_VERSION: v0.64.1
 
+# Define stages - extends Prosper's stages with our custom ones
+stages:
+  - .pre
+  - lint
+  - build
+  - test
+  - deploy
+
 kics:
   allow_failure: true