ServiceLevelObjectiveHistory generates error during unmarshalling

[Atilla-Bilgic]

Many thanks for your effort to build this flawless component. I hope this contribution may help to improve.

The struct definition for .data.series.denominator.metadata.unit needs to be replaced by an interface or another struct definition.
Sample data returned from Datadog through their API that crashes the component can be seen below.
******** Sample Data ********
"metadata": {
"unit": [
{
"family": "network",
"scale_factor": 1.0,
"name": "request",
"short_name": "req",
"plural": "requests",
"id": 19
},
null
],
...}
******* End of Sample *****