Document rules for upgrading CSC servers

[nharraud]

Problem:
We need to have a workflow and a set of rules explaining which conditions are required to update training and production servers.
The goal is to improve our worklows and crash recovery time.

Example of information:

• The first step of any B2SHARE release is to deploy it on a test server. This test server should have a backup of b2share.eudat.eu loaded in order to test the migration.
• The training server is used by EUDAT users and communities. The data should not be wiped and it should only be updated when a new release of B2SHARE has been tested on a test server.
• Send an email to ... which is in charge of backups at CSC in order to have them ready before upgrading the server. (getting a backup of the files can take some time).

I suggest to create a wiki page on this repository.

@emanueldima @Tlacahuepan @thijscobben @SarahBA @dinosk