feat: Add generic database connection mechanism (#754)

* feat: Implement generic database connection

* fix: Add to Pod template as well

* Bump op-rs

* Fix tests

* Update kuttl tests

Co-authored-by: Andrew Kenworthy <andrew.kenworthy@stackable.tech>

* Update docs

Co-authored-by: Andrew Kenworthy <andrew.kenworthy@stackable.tech>

* Further update docs

* bump op-rs

* cargo fmt

* Use docs from op-rs

* Bump op-rs

* Impl Deref for database connection enums

* Some docs

* Rename celeryResultBackend -> ResultBackend and celeryBroker -> broker

* WIP changelog

* changelog

* changelog

* Fix some leftover credentialsSecret renames

* test: Fix ca-cert test

* More test fixes

* Fix more tests

* Update tests/templates/kuttl/versioning/30-install-airflow-cluster.yaml.j2

Co-authored-by: Andrew Kenworthy <1712947+adwk67@users.noreply.github.com>

* yaml linter

---------

Co-authored-by: Andrew Kenworthy <andrew.kenworthy@stackable.tech>
Co-authored-by: Andrew Kenworthy <1712947+adwk67@users.noreply.github.com>

Author: sbernauer

CHANGELOG.md

@@ -13,6 +13,11 @@
 - BREAKING: `configOverrides` now only accepts the known config file `webserver_config.py`. Previously, arbitrary file names were silently accepted and ignored ([#775]).
 - Bump `stackable-operator` to 0.110.1, kube to 3.1.0, and snafu to 0.9 ([#775]).
 - BREAKING: Rename `EXPERIMENTAL_FILE_HEADER` and `EXPERIMENTAL_FILE_FOOTER` in `webserver_config.py` for arbitrary python code to `FILE_HEADER` and `FILE_FOOTER`  ([#775], [#777]).
+- BREAKING: The `.clusterConfig.credentialsSecret` field has been renamed to `.clusterConfig.credentialsSecretName` for consistency ([#754]).
+- BREAKING: Implement generic database connection.
+  This means you need to replace your simple database connection string with a typed struct.
+  This struct is consistent between different CRDs, so that you can easily copy/paste it between stacklets.
+  Read on the [Airflow database documentation](https://docs.stackable.tech/home/nightly/airflow/usage-guide/database-connections) for details ([#754]).
 
 ### Fixed
 
@@ -25,6 +30,7 @@
 [#774]: https://github.com/stackabletech/airflow-operator/pull/774
 [#775]: https://github.com/stackabletech/airflow-operator/pull/775
 [#777]: https://github.com/stackabletech/airflow-operator/pull/777
+[#754]: https://github.com/stackabletech/airflow-operator/pull/754
 
 ## [26.3.0] - 2026-03-16