Fix for the manifest file size validation to follow OSDU API implementation

This is not a permanent fix but would make the validation selection better.

We are adding the implementation of OSDU API of having indent=4 so that we have more padding, and the calculation is handled in-front rather than behind (at OSDU API)

Relevant issue:

OSDU Fetch & Ingest failing with "ConnectionResetError" when the record size more than 1MB (#349) · Issues

RequestBodyTooLarge exception in EDS ingest for large payload. (#125) · Issues