[HWORKS-250] Add compatibility with hsml 3.0.*

Author: javierdlrm

hopsworks-api/src/main/java/io/hops/hopsworks/api/modelregistry/models/dto/ModelDTO.java

@@ -76,6 +76,8 @@ public ModelDTO() {
   private Integer modelRegistryId;
 
   private TagsDTO tags;
+  
+  private String type = "modelDTO";
 
   public String getName() {
     return name;
@@ -216,11 +218,13 @@ public void setModelRegistryId(Integer modelRegistryId) {
   public TagsDTO getTags() {
     return tags;
   }
-
+  
   public void setTags(TagsDTO tags) {
     this.tags = tags;
   }
-
+  
+  public String getType() { return type; }
+  
   @Override
   public String toString() {
     return "ModelDTO{" +

hopsworks-api/src/main/java/io/hops/hopsworks/api/serving/ServingUtil.java

@@ -145,7 +145,11 @@ private void validateModelVersion(Serving serving) {
 
   private void validateModelFramework(Serving serving) {
     if (serving.getModelFramework() == null) {
-      throw new IllegalArgumentException("Model framework not provided");
+      serving.setModelFramework(serving.getModelServer() == ModelServer.TENSORFLOW_SERVING ?
+        ModelFramework.TENSORFLOW : ModelFramework.SKLEARN);
+      // backward compatibility with hsml 3.0 (which does not send model framework value)
+      // greater versions hsml and UI should not send null values
+      return;
     }
     if (serving.getModelFramework() == ModelFramework.TENSORFLOW
       && serving.getModelServer() != ModelServer.TENSORFLOW_SERVING) {