panic while accessing undefined cf metadata annotations/labels

[cbarbian-sap]

In a couple of places we evaluate cf metadata annotations or labels like

parameterHash := *serviceInstance.Metadata.Annotations[annotationParameterHash]

(https://github.com/SAP/cf-service-operator/blob/main/internal/cf/instance.go#L43)

Under normal circumstances, this does not cause a problem, since the logic in cf-service-operator ensures that the labels/annotations were properly set, before reading them for the first time. However, in case someone changed things manually in the cf api, or if existing instances/bindings were incompletely adopted, the code might dereference a nil pointer, and therefore panic.

This should be handled in a more robust way. Proposal: have a wrapper method for accessing cf labels/annotations which first checks if the according key exists and the respective value is non-nil, and only then dereferences it.