Improve error messages from create_note

What does this MR do?

The design of create_note meant that it would fail correctly, but with very un-informative error messages. This re-write of the method means that we raise the validation error to the programmer with details of what the problem actually is.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and testing

This does not change the behaviour of the code.

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.