Add 1.0.0 upgrading hints

doc/80-Upgrading.md

@@ -3,6 +3,36 @@
 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. We have dropped the `start` and `frequency`
+columns of the `schedule` table. Please find the upgrade script in **schema/*-upgrades**.
+
+> **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, the two columns will
+> be dropped, and you won't be able to restore your 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
+
+Since we're not going to use the `start` and `frequency` columns any longer in version `1.0.0`, you need to migrate the
+data stored in those columns first before importing the upgrade script. To do this, please run the following command.
+
+```bash
+icingacli reporting migrate schedules
+```
+
+Only when this command returns successfully, you can apply the upgrade script, which will then drop those no longer
+used columns.
+
+```bash
+# mysql -u root -p reporting <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.