[FEAT] Fetch Missing Values from Management Portal REST API When Saving User

[this-Aditya]

Description: When saving a user to the database, if any value is null and can be retrieved from the Management Portal, fetch the missing value using the Management Portal API. For example: If only subject Id is present then other values like projectId etc can be fetched from MP using API.

Prerequisite: Before implementing this functionality, ensure support for Management Portal APIs has been added. For more details, refer to the related issue: #521

[yatharthranjan]

The app server was created with de-coupling in mind, so it does not rely on any entity management system; this way, MP or any other system is readily swappable. This is more important now as we get rid of the management portal that is in favour of Ory. But I agree it would be nice to support the external state store to keep things consistent and not have to maintain the same state in 2 places. This should be handled after moving from spring to Jersey as radar-jersey library already supports this using project and user service components.

[this-Aditya]

Okay, I created this issue because it was commented as a to-do in code. Yes, it would be nice to tackle this after shifting to Jersey.