feat(known-issue): add hard delete of instance in case of issue

docs/easycozy/known_errors.md

@@ -7,4 +7,21 @@ On the server, we can see that the server is underwater by using "top" command:
 ![oops_error_1](/img/known_errors/oops_error_1.png)
 
 To fix this issue, just restart the service on the server with "docker-compose down / docker-compose up -d" in the easy-cozy folder:
-![oops_error_2](/img/known_errors/oops_error_2.png)
+![oops_error_2](/img/known_errors/oops_error_2.png)
\ No newline at end of file
+
+### Impossible instance delete 
+
+When you get this issue after trying to delete instance :
+
+![delete_issue](/img/known_errors/instance_delete_issue.png)
+
+You have to remove it from db, in order to do that follow this steps :
+
+1. Get instance UUID
+```sh
+docker-compose exec cozy ./cozy instances show-db-prefix --host 0.0.0.0 demo.cozy.self-data.alpha.grandlyon.com
+```
+
+2. Connect to database with ssh port forwarding or use curl requests
+
+3. Remove instance in `gloabal/instances` db by searching for UUID. (Ex: cozy5e2af113e04eb2319ef1b7645c5790e1)