Add 1.0.0 upgrading docs

doc/80-Upgrading.md

@@ -3,6 +3,39 @@
 Upgrading Icinga Reporting is straightforward.
 Usually the only manual steps involved are schema updates for the database.
 
+## Upgrading to Version 1.0.0
+
+Icinga Reporting version 1.0.0 requires a schema update for the database.
+
+> **Warning**
+>
+> If you're not using Icinga Web 2 version `>= 2.12`, it's essential that you perform the migration steps in the
+> exact order as described below. Otherwise, if you import the migration script before running the cli command,
+> you won't be able to restore your report schedule config.
+
+If you're already using Icinga Web 2 version `>= 2.12`, then you don't need to perform any of these steps manually. Icinga
+Web 2 provides you with the ability to perform such migrations in a simple way. You may be familiar with such an automation
+if you're an Icinga Director user. For those who are not using the latest version of Icinga Web 2, please follow the
+instructions below.
+
+You need to run the following cli command before importing the upgrade script.
+
+```
+# icingacli reporting migrate schedules
+```
+
+Only when this command returns successfully, you can apply the upgrade script.
+Please find the upgrade script in **schema/*-upgrades**.
+<!-- {% if not icingaDocs %} -->
+
+**Note:** If you haven't installed this module from packages, then please adapt the schema path to the correct installation path.
+
+<!-- {% endif %} -->
+
+```
+# mysql -u root -p reporting /usr/share/icingaweb2/modules/x509/schema/mysql-upgrades/1.0.0.sql
+```
+
 ## Upgrading to Version 0.10.0
 
 Icinga Reporting version 0.10.0 requires a schema update for the database.