Fix #34605: add docker-group-add

Author: LEDfan

src/main/java/eu/openanalytics/containerproxy/backend/docker/DockerEngineBackend.java

@@ -186,6 +186,8 @@ public Proxy startContainer(Authentication user, Container initialContainer, Con
                     .build());
             }
 
+            hostConfigBuilder.groupAdd(spec.getDockerGroupAdd().getValueOrNull());
+
             ContainerConfig containerConfig = ContainerConfig.builder()
                 .hostConfig(hostConfigBuilder.build())
                 .image(spec.getImage().getValue())

src/main/java/eu/openanalytics/containerproxy/model/spec/ContainerSpec.java

@@ -88,6 +88,8 @@ public class ContainerSpec {
     @Builder.Default
     private SpelField.String dockerIpc = new SpelField.String();
     @Builder.Default
+    private SpelField.StringList dockerGroupAdd = new SpelField.StringList();
+    @Builder.Default
     private List<DockerDeviceRequest> dockerDeviceRequests = new ArrayList<>();
 
     @Builder.Default
@@ -134,6 +136,7 @@ public ContainerSpec firstResolve(SpecExpressionResolver resolver, SpecExpressio
             .dockerRuntime(dockerRuntime.resolve(resolver, context))
             .dockerUser(dockerUser.resolve(resolver, context))
             .dockerIpc(dockerIpc.resolve(resolver, context))
+            .dockerGroupAdd(dockerGroupAdd.resolve(resolver, context))
             .build();
     }