Consider deleting/invalidating status.yml files on service instance updates

[JohannesRudolph]

Some service owners building services on top of unipipe-service-broker may want to support parameter updates on existing service instances, or even mark their services plan_updateable.

In this scenario we should consider invalidating the status.yml file, possibly by deleting it. Without this additional invalidation the behavior of unipipe-service-broker would be inconsistent as it would return the last status written by the pipeline (e.g. a "succeeded") when in fact the pipeline has not yet processed the update to the service instance.

There's already existing logic for returning a default last operation state in that case:

unipipe-service-broker/src/main/kotlin/io/meshcloud/dockerosb/service/GenericServiceInstanceService.kt

Lines 96 to 106 in 3acc472

	var status = OperationState.IN_PROGRESS
	var description = "preparing deployment"
	if (statusYml.exists()) {
	val retrievedStatus = yamlHandler.readObject(statusYml, Status::class.java)
	status = when (retrievedStatus.status) {
	"succeeded" -> OperationState.SUCCEEDED
	"failed" -> OperationState.FAILED
	else -> OperationState.IN_PROGRESS
	}
	description = retrievedStatus.description
	}

I'm not sure about the impact on service bindings, but maybe there are similar concerns for them.

[JohannesRudolph]

Closed via #129