Extend init_containers defined in pod_override

[repocho]

If you add an init_container in pod_override the specified init_containers in the pod-template-file for kubernetes are ovewritten instead of extended as it is the case of the volumes for example.
So, for example, if you have a git sync ini_container but you define another init container, the task won't be executed because airflow won't find the dags as the init_container is replaced.

This change is just extending the init_container defined in the pod_override with the existing ones defined in the pod template file for kubernetes. In that sense you can define new extra init_containers.

[boring-cyborg]

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[jedcunningham]

Thanks @repocho! Can you add a test for this in tests/kubernetes/test_pod_generator.py?

[repocho]

Thanks for the time reviewing this PR @jedcunningham !

I have added a test for this. Let me know if you need anything more.
Thanks again.

[repocho]

Thanks @jedcunningham, I have merged your suggestions and launched the tests again with success.

tests/kubernetes/test_pod_generator.py::TestPodGenerator::test_reconcile_specs_init_containers PASSED 

[jedcunningham]

Oh, looks like we have a static check failure in that test file. Can you reformat that when you get the chance?

[github-actions]

The PR most likely needs to run full matrix of tests because it modifies parts of the core of Airflow. However, committers might decide to merge it quickly and take the risk. If they don't merge it quickly - please rebase it to the latest main at your convenience, or amend the last commit of the PR, and push it with --force-with-lease.

[repocho]

I have rebased the branch with the last changes in branch main, to be able to launch all the tests

[boring-cyborg]

Awesome work, congrats on your first merged pull request!

[jedcunningham]

Thanks for the bugfix @repocho and congrats on your first commit 🎉!

[repocho]

Thank you for all your help !! 😉