Upgrade process

[Keoghan]

A placeholder for now, that we should consider how we can make this as painless as possible.

[rdarcy1]

• Pull from git
• Clean out old images if necessary
• Copy new files if necessary
• Pull/build new container images

[rdarcy1]

Create 'migrations' for each release which alter user directory files (config, database migrations etc).

Back up files that will be affected. Delete automatically after successful upgrade? Or delete after a delay, maybe 7 days after upgrade?

[Keoghan]

Also composer install