Introduce subclasses of IrisWarning to precisely categorise all the types of warning relating to Iris behaviour. This will enable easy suppression of specific types of warning if a user knows this does not matter for their workflow.

Worldwide recognised warning categories - e.g. DeprecationWarning - should keep these categorisations and not be brought into the IrisWarning hierarchy.

Illustrative examples

• IrisWarning
  • CFWarning
    • NotStdNameWarning
    • MissingCoordWarning
  • DemotedCoordWarning