Configure SAST in `.gitlab-ci.yml`, creating this file if it does not already exist

.gitlab-ci.yml

+# You can override the included template(s) by including variable overrides
+# SAST customization: https://docs.gitlab.com/ee/user/application_security/sast/#customizing-the-sast-settings
+# Secret Detection customization: https://docs.gitlab.com/ee/user/application_security/secret_detection/#customizing-settings
+# Note that environment variables can be set in several places
+# See https://docs.gitlab.com/ee/ci/variables/#priority-of-environment-variables
 test:php7_latest:
   image: php:7
   script:
-    - apt update -yqq && apt install git zip -yqq
-    - git submodule init
-    - git submodule update
-    - php --version
-    - ./vendor/bin/phpunit -c tests/phpunit.xml --testdox
+  - apt update -yqq && apt install git zip -yqq
+  - git submodule init
+  - git submodule update
+  - php --version
+  - "./vendor/bin/phpunit -c tests/phpunit.xml --testdox"
   except:
-    - tags
+  - tags
   tags:
-    - docker
+  - docker
+stages:
+- test
+sast:
+  stage: test
+include:
+- template: Security/SAST.gitlab-ci.yml