Support Kolla image tags overrides per environment

[grzegorzkoper]

No description provided.

[gemini-code-assist]

Code Review

This pull request introduces support for overriding Kolla image tags per environment, enhancing flexibility in deployment configurations. The changes involve updating documentation in etc/kayobe/kolla/globals.yml and tools/kolla-images.py to reflect this new capability. The Python script tools/kolla-images.py has been refactored to include new functions for reading, merging, and loading image tags from both a base file and an optional environment-specific override file. This refactoring improves modularity and robustness, with appropriate error handling for missing or invalid tag configurations. The overall change is a positive step towards more dynamic and environment-aware image tag management.

[Alex-Welsh]

I'll do a full review some other time, but I just want to mention:

1. This is a really nice feature
2. The Python component of SKC is starting to grow. I think that's a good thing. Ansible is great for some tasks but can become a complete mess when you try to do anything complicated. But we should think about python unit tests & linting
3. needs a reno

[grzegorzkoper]

I'll do a full review some other time, but I just want to mention:

1. This is a really nice feature
2. The Python component of SKC is starting to grow. I think that's a good thing. Ansible is great for some tasks but can become a complete mess when you try to do anything complicated. But we should think about python unit tests & linting
3. needs a reno

1. Thanks
2. Good point, something that K/A and Kayobe already are doing - worth checking there for inspiration ?
3. Done