Read measured public-goods metrics

{  "generatedAt": "2019-08-24T14:15:22Z",  "publication": {    "observedAt": "2019-08-24T14:15:22Z",    "configuredDatasets": 0,    "publishedDatasets": 0,    "completedBatches": "string",    "failedBatches": "string",    "startedBatches": "string",    "records": "string",    "latestCompletedAt": "2019-08-24T14:15:22Z",    "maximumLedger": "string"  },  "archives": {    "observedAt": "2019-08-24T14:15:22Z",    "knownRoots": 0,    "checkedRoots": 0,    "checkedRootWindowHours": 24,    "rootObjectsVerified": 0,    "rootObjectsFailed": 0,    "oldestEvidenceAt": "2019-08-24T14:15:22Z",    "newestEvidenceAt": "2019-08-24T14:15:22Z",    "complete": true  }}