Feature request: Allow running against a locally deployed DICOMweb endpoint

[jasonklotzer]

It looks like the code requires a service account for Healthcare API by default, which may not be supplied if someone is trying to run the adapter using local DIMSE and DICOMweb services, primarily in a testing/development environment.

At first glance it seems the remedy, at least for the DIMSE->STOW-RS mode (pub/sub has not been tested), is to put some logic around the following line:
https://github.com/GoogleCloudPlatform/healthcare-dicom-dicomweb-adapter/blob/master/import/src/main/java/com/google/cloud/healthcare/imaging/dicomadapter/ImportAdapter.java#L92, only including new HttpCredentialsAdapter(credentials) when necessary?

The error and stack that show up when trying to run the adapter w/o a service account:

ERROR com.google.cloud.healthcare.imaging.dicomadapter.CStoreService - C-STORE request failed:
com.google.cloud.healthcare.IDicomWebClient$DicomWebException: java.io.IOException: Scopes not configured for service account. Scoped should be specified by calling createScoped or passing scopes to constructor.
at com.google.cloud.healthcare.DicomWebClient.stowRs(DicomWebClient.java:132)
at com.google.cloud.healthcare.imaging.dicomadapter.CStoreService.lambda$store$3(CStoreService.java:129)
at com.google.cloud.healthcare.imaging.dicomadapter.CStoreService.processStream(CStoreService.java:174)
at com.google.cloud.healthcare.imaging.dicomadapter.CStoreService.store(CStoreService.java:137)
at org.dcm4che3.net.service.BasicCStoreSCP.onDimseRQ(BasicCStoreSCP.java:72)
at org.dcm4che3.net.service.DicomServiceRegistry.onDimseRQ(DicomServiceRegistry.java:86)
at org.dcm4che3.net.ApplicationEntity.onDimseRQ(ApplicationEntity.java:474)
at org.dcm4che3.net.Association.onDimseRQ(Association.java:713)
at org.dcm4che3.net.PDUDecoder.decodeDIMSE(PDUDecoder.java:467)
at org.dcm4che3.net.Association.handlePDataTF(Association.java:696)
at org.dcm4che3.net.State$4.onPDataTF(State.java:103)
at org.dcm4che3.net.Association.onPDataTF(Association.java:692)
at org.dcm4che3.net.PDUDecoder.nextPDU(PDUDecoder.java:177)
at org.dcm4che3.net.Association$2.run(Association.java:529)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:835)
Caused by: java.io.IOException: Scopes not configured for service account. Scoped should be specified by calling createScoped or passing scopes to constructor.
at com.google.auth.oauth2.ServiceAccountCredentials.refreshAccessToken(ServiceAccountCredentials.java:390)
at com.google.auth.oauth2.OAuth2Credentials.refresh(OAuth2Credentials.java:157)
at com.google.auth.oauth2.OAuth2Credentials.getRequestMetadata(OAuth2Credentials.java:145)
at com.google.auth.http.HttpCredentialsAdapter.initialize(HttpCredentialsAdapter.java:91)
at com.google.api.client.http.HttpRequestFactory.buildRequest(HttpRequestFactory.java:88)
at com.google.api.client.http.HttpRequestFactory.buildPostRequest(HttpRequestFactory.java:128)
at com.google.cloud.healthcare.DicomWebClient.stowRs(DicomWebClient.java:125)
... 16 more