chore: Use anchors in regular expressions

[siegfriedweber]

Description

Use the anchors ^ and $ in regular expressions

In stackable-operator and in the Kubernetes source code, there are formats (fmt), e.g. [a-z]([-a-z0-9]*[a-z0-9])?, and regular expressions (regex), e.g. ^[a-z]([-a-z0-9]*[a-z0-9])?$. The format is without anchors and the regular expression contains the anchors (if desired).

This is now applied to the regular expressions in this operator.

The constants from stackable-operator are not used anymore because strings cannot be concatenated at compile-time. This would be possible with a macro like concatcp but I chose, not to introduce another dependency.

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
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Author

• Integration tests passed (for non trivial changes)

Reviewer

• Code contains useful comments
• Code contains useful logging statements
• (Integration-)Test cases added
• Documentation added or updated. Follows the style guide.
• Changelog updated
• Cargo.toml only contains references to git tags (not specific commits or branches)

Acceptance

• Feature Tracker has been updated
• Proper release label has been added
• Links to generated (nightly) docs added
• Release note snippet added
• Add type/deprecation label & add to the deprecation schedule
• Add type/experimental label & add to the experimental features tracker

[labrenbe]

lgtm