Property side-effects with @lt.on_set

[rwb27]

This adds basic side-effects to properties, along with some tests.

Methods may be decorated with @lt.on_set. The method will then be run whenever the property is set.

To-do:

• Add to public API docs
• Add to conceptual docs on data properties, and link from functional properties
• Test this against DataSetting as well as properties

This is intended to allow for basic validation or synchronisation, where the full power of a functional property is not needed. It runs before validation (if enabled), to allow coercion and to catch None in case someone's forgotten to return a value from on_set. This could become configurable in the future.

It may be desirable to also allow a similar decorator to add a validator to the Pydantic model, but that might require more thought, and is not for this PR.

Closes #237

[barecheck]

Barecheck - Code coverage report

Total: 96.68%

Your code coverage diff: -0.06% ▾

Uncovered files and lines

File	Lines
src/labthings_fastapi/properties.py	464, 482, 562, 925-926, 928, 968, 972, 1007-1010, 1082, 1105, 1504

[rwb27]

From @julianstirling out-of-band:

• Simulation camera updates the canvas on certain propery changes
• Also when we have mapping thingslots we check if the key is available in the mapping when we change our selectors