"dotted.key" config might get unflatten in json config

[phuongfi91]

Given the following json config

  "existing_key": "existing_value",

If a key-value is missing according to styling config and the key has dotted format (e.g. dotted.key)

  "dotted.key": """
     "some_value"
  """

This would add the missing key-value, but incorrectly unflatten it due to the presence of dot notation:

  "existing_key": "existing_value",
  "dotted": {
     "key": "some_value"
   }

Workaround:
In styling config, wrap the key with double single quotes:

  "''dotted.key''": """
     "some_value"
  """

This way the output config would preserve the key format:

  "existing_key": "existing_value",
  "dotted.key": "some_value"

The reason why we need two pair of single quotes is because the key got unflatten twice in the code