Description

This PR proposes the following changes to the private _utils.parse_harmonic function:

1. Replace samples with harmonic_max parameter to make the function more consistent and easier to understand.
2. Make harmonic_max parameter optional to allow for cases where the upper harmonics limit is unknown (as in Simplify multiple harmonic calibration #124).

This simplifies existing code a little.

Also added a note to the phasor_from_signal function that "A minimum of harmonic * 2 + 1 samples are required along axis to calculate correct phasor coordinates at harmonic". This is actually not verified in parse_harmonic and Fourier transform does return second harmonic numbers for 4 samples even though they are not correct phasor coordinates (as far as I understand). There is however a verified requirement for an absolute minimum of three signal samples.

Checklist

• The pull request title and description are concise.
• Related issues are linked in the description.
• New dependencies are explained.
• The source code and documentation can be distributed under the MIT license.
• The source code adheres to code standards.
• New classes, functions, and features are thoroughly tested.
• New, user-facing classes, functions, and features are documented.
• New features are covered in tutorials.
• No files other than source code, documentation, and project settings are added to the repository.