Adds rule to check if each panel has valid units assigned

[mshahzeb]

Reference issue:
#51

This rule checks that each panel must have a valid unit assigned.
The unit is extracted from dashboard json in the following manner:

• Parse overrides to check if any override unit is present
• If no overrride unit - then extract standard option unit
• Check if unit is defined and is valid

Valid units are extracted from here:
https://github.com/grafana/grafana/blob/main/packages/grafana-data/src/valueFormats/categories.ts

Considerations:

• For a panel with multiple fields and panels - the last override unit will be picked

Sample output:

[CLAassistant]

All committers have signed the CLA.

[mshahzeb]

Since the override value is of dynamic type - It can be an int or a string.

I am getting an error in case when a dashboard has mixed int and string values in overrides.
I am working on a fix for that too.

[mshahzeb]

Should we leave none as an allowed unit to be set if no other unit makes sense?

Or remove this and let the user add a lint exclusion in that case?

[rgeyer]

I wasn't sure the behavior for a default dashboard/panel, so I just tested it.

When a new panel is created, with no config, no unit is set. Literally the unit property is absent in fieldConfig.

In the dropdown/picker for units, none does not appear to be an option. If you type it in manually, you can set it as a "custom" unit.

For this reason, I would say this shouldn't be an allowed valid unit, and if users choose to explicitly specify "none" they should also create a lint exclusion rule.

[rgeyer]

LGTM, with the one bit of feedback on the "none" unit type.

Great work. Thank you!

[rgeyer]

I wasn't sure the behavior for a default dashboard/panel, so I just tested it.

When a new panel is created, with no config, no unit is set. Literally the unit property is absent in fieldConfig.

In the dropdown/picker for units, none does not appear to be an option. If you type it in manually, you can set it as a "custom" unit.

For this reason, I would say this shouldn't be an allowed valid unit, and if users choose to explicitly specify "none" they should also create a lint exclusion rule.