This CredentialProvider implementation extends the DefaultCredentialProvider by searching the GCP Secrets Manager for the named secret. A BasicCredential will be returned containing the string value. A projectId is required to instantiate.
When creating the secret that will be used, there are several properties that will be considered. Since GCP Secrets Manager takes a single value, when storing the JSON service account key, it should be stored as JSON. The same is applicable when storing AWS keys. The data should not be encoded.