Currently, in the template, any empty container gets removed.

Apparently, there is a need to actually send empty container in some cases.

With this change, keeping EMPTY_CONTAINER keyword will cause the empty container and appear in the resulting JSON.

Example:

Template:

{
    "container1": {},
    "container2": EMPTY_CONTAINER
}

It will result in the following JSON:

{
    "container2": {}
}