update service section

docs/ecolyo/application/services.md

-!!! warning ""
-    :construction: Section under Construction :construction:
-
 ## Cron Services
 
 In order to build an automated task within our cozy-stack, we can create *services* which are javascript files called from a trigger job.
@@ -15,12 +12,28 @@ File location is determined after the build, see [here](https://forge.grandlyon.
 !!! note "Cron"
     See the cron definition at [cozy-stack](https://docs.cozy.io/en/cozy-stack/jobs/#cron-syntax).
 
-### Services
+## Ecolyo services
 
 Located under **src\targets\services**
 
-#### Monthly report notification
+### Monthly report notification
+
+#### Definition of the service
+The service will run the 3rd of each month at 10.00 am, as defined in the manifest:
+
+```
+"monthlyReportNotification": {
+      "type": "node",
+      "file": "services/monthlyReportNotification/ecolyo.js",
+      "trigger": "@cron 0 0 10 3 * *"
+    }
+```
+#### Main responsabilities of the service
 
-Fetches metadata to customize the mail (Public name, instance url).
+The service is reponsible of sending a mail to user to warn him about the availability of a new information in the Analyse.
 
-Send mail containing a link to the user instance so that he can be warned about the update of its monthly report and visualize it.
+Main steps are the following:
+ - Check the "sendReportNotification" attribute in the com.grandlyon.ecolyo.profile doctype. If true, service will continue, else it will stop.
+ - Fetches metadata to customize the mail (Public name, instance url).
+ - Build the mail.
+ - Send the mail.