add gitlab check in check_http

docs/20_Checks/check_http.md

@@ -117,7 +117,6 @@ Found:
 You can set the method with ``-m``.
 ``./check_http -m head -u https://www.example.com/`` responds
 
-
 ```txt
 OK: HEAD https://www.example.com/ (200)
 
@@ -152,6 +151,10 @@ You can verify if the response matches a given regex. You can search in the resp
 With the parameter ``-j JQ-FILTER`` the jq command will be applied on the response body.
 Whenever you add ``-j`` a search in the body with params ``-b REGEX`` and ``-n REGEX`` won't be applied to the complete response body but on the result after filtering with jq. So you can build API checks that respond a json structure.
 
+#### Keycloak
+
+See <https://www.keycloak.org/server/health>
+
 Keycloak responds on its health url
 
 ```txt
@@ -184,3 +187,51 @@ Hints:
 Content after jq filter: "UP"
 
 ```
+
+#### Gitlab
+
+See <https://docs.gitlab.com/ee/administration/monitoring/health_check.html>
+
+Gitlab allows requests to localhost for the health check.
+You can use these command lines:
+
+Health check:
+
+```txt
+./check_http  -u localhost/-/health -b "Gitlab OK" 
+OK: GET localhost/-/health (200)
+
+Found:
+- Http status is a 2xx OK [200]
+- [Gitlab OK] was found in body
+```
+
+Raediness:
+
+```txt
+./check_http -u 'http://localhost/-/readiness' -j '.master_check[] .status' -b 'ok'
+OK: GET http://localhost/-/readiness (200)
+
+Found:
+- jq filter [.master_check[] .status] matches
+- Http status is a 2xx OK [200]
+- [ok] was found in body
+
+Hints:
+Content after jq filter: "ok"
+```
+
+Liveness:
+
+```txt
+./check_http -u 'http://localhost/-/liveness' -j '.status' -b 'ok'
+OK: GET http://localhost/-/liveness (200)
+
+Found:
+- jq filter [.status] matches
+- Http status is a 2xx OK [200]
+- [ok] was found in body
+
+Hints:
+Content after jq filter: "ok"
+```