refactor: update docker login command in ci_staging.gitlab-ci.yml to use...

refactor: update docker login command in ci_staging.gitlab-ci.yml to use password-stdin for improved security

capif/templates/ci_staging.gitlab-ci.yml

@@ -338,7 +338,7 @@ staging_build_and_push_mr:
    - export TMP_PWD=$PWD
    - echo "TMP_PWD=$TMP_PWD"
    - echo "### docker login###"
-   - docker login --username $CI_REGISTRY_USER --password $CAPIF_DOCKER_REGISTRY $CI_REGISTRY
+   - echo "$CI_JOB_TOKEN" | docker login $CI_REGISTRY --username $CI_REGISTRY_USER --password-stdin
    - echo "----------------------------------------------------"
    - echo "### build and push nginx image###"
    - cd $TMP_PWD/services/nginx/