Nested Map JSON Schema 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):
  This PR adds the support for the deserialisation of a json that can have a nested map property. This is needed during the schema filter and the schema creation stages. Once accurate JSON is created, the subsequent operations for data write work fine since Avro already has support for nested json schema.

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:
  Done with some of the existing flows.

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"