[FEATURE] Update MCA Update to process additional merchant data for open banking connectors

[Sarthak1799]

Feature Description

Currently, we only accept additional_merchant_data in the MCA create req, we need to accept it in update req as well and and add the logic for processing the data in the MCA update core.

Possible Implementation

Need to update the relevant api_models and core logic

Have you spent some time checking if this feature request has been raised before?

• I checked and didn't find a similar issue

Have you read the Contributing Guidelines?

• I have read the Contributing Guidelines

Are you willing to submit a PR?

Yes, I am willing to submit a PR!