Adding enum for nested json support

[gautamshanu]

Dear DIL maintainers,

Please accept this PR. I understand that it will not be reviewed until I have checked off all the steps below!

JIRA

• My PR addresses the following JIRA issues and references them in the PR title.

Description

• Here are some details about my PR, including screenshots (if applicable):

For JsonExtractor, while fetching the schema as part of extraction, we set the row filter.
This row filter is a JsonSchemaBasedFilter. For this, we try to convert each element from the output schema of the job configs into a JisColumn.
This needs us to set the data type. When this type is a map, the flow fails, because we don't have a MAP type under JsonElementTypes to set as the data type.

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

Commits

• My commits all reference JIRA issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

[avinas-kumar]

LGTM