Upgrade - change the upgrade and migration process

[crssnd]

What should be investigated. Automate the upgrade process by creating scripts instead of code snippets to be run manually. Separate the init and config steps from the apply steps and scripts as the CD solution should only run the apply steps and scripts.

Definition of done:

1. a process on how and who should create this migration scripts, separated config and apply scripts
2. create templates for the migration scripts that can be reused for the main or patch releases
3. template migration scripts for how to change yaml config in apps
4. add the test steps in a script to run before and after the upgrade

[cristiklein]

Folks, I upgraded the demo environment to v0.19.0. I feel the migration scripts are going in the right direction.

I have the following suggestions on how to move forward.

1. Number the scripts in the order in which an administrator is expected to run them, e.g., 10_migrate_to_opensearch.sh.
2. Put the instructions as comment (or strings) as the start of each migration scripts. Then the "main" migration script could be as simple as for $SCRIPT in [0-9][0-9]*.sh; do ./$SCRIPT; done.

My 2 cents.