chore: Release stackable-operator 0.78.0

[adwk67]

Description

Added/Changed

• Add Kerberos AuthenticationProvider ([feat: add kerberos authentication provider #880]).

This is a breaking change as match statements that check for values of pub enum AuthenticationClassProvider will need to consider the new case.

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

Author

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1. Changes are OpenShift compatible
2. CRD changes approved
3. Integration tests passed (for non trivial changes). Tested with Kafka/Kerberos.

Reviewer

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1. Code contains useful comments
2. (Integration-)Test cases added
3. Documentation added or updated
4. Changelog updated
5. Cargo.toml only contains references to git tags (not specific commits or branches)

Acceptance

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1. Feature Tracker has been updated
2. Proper release label has been added

[Techassi]

One could argue we just do a patch release instead of a minor release, but I guess it's fine anyway.

[sbernauer]

We add a new enum variant, isn't this breaking? (I 100% know it will break some operators)