Add ensure_cdk macro for validation checks

[ok300]

Description

This PR brings the ensure_cdk macro, which is similar to anyhow::ensure.

It lets us replace validation steps like

if !flag {
  return Err(CustomError::Type);
}

with

ensure_cdk!(flag, CustomError::Type);

which helps make with code more readable and maintainable.

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Suggested CHANGELOG Updates

CHANGED

ADDED

• Improve code readability: introduce ensure_cdk

REMOVED

FIXED

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Checklist

• I followed the code style guidelines
• I ran just final-check before committing

[thesimplekid]

Nice one