Let's Apply YAML editor in model-serving

[lizable]

Main idea

Since the model service executes its service based on model-definition.yml file, we need to provide an editable UI for the YAML file. With YAML editor, user can edit freely and notice any typo or wrong indentations, without creating a new session to mount and check the file when an error occurs during model service execution because of YAML file error.

Here's the image of error message when the content in model-definition.yml file is invalid.

We already have YAML editor in Backend.AI FastTrack, I think we can make it as "shared components".

Alternative ideas

We could first apply user-friendly UI modal for creating/storing model-definition.yml file as a workaround of YAML editor.

Anything else?

No response

[lizable]

I presume we need corresponding server-side implementation (such as open YAML file and save YAML file.) What do you think? @achimnol @kyujin-cho