[GIG][API] GraphQL PoC for OrgChart App

[vibhatha]

Description

OrgChart App contains a diverse range of queries.

A few of the very basic queries already supported in the OrgChart v1 are as follows.

1. Retrieve ministers of a particular moment in time
2. Retrieve departments associated with ministers of a particular moment in time
3. Retrieve a particular department and see under which ministers it was held in the past

But the user should be able to query the following as well

1. Retrieve a minister who has managed a particular department in combination with another department in a particular period.
2. Retrieve the department and find out which ministers have managed it during a set of non-consecutive time ranges.

When such queries need to be executed, more filters are required meaning the query gets complex. REST API usage is not practical for such cases. This should be able to resolve by adopting the GraphQL API.

Goals

1. Enable complex query specification for a single API call
2. Determine a pool of such queries and define a specification that could cover more ground for future queries.

Non Goals

1. Replace REST API usage in the project 100%
2. Writing a production-ready solution.

Motivation

Provide powerful APIs for application development not just for the applications developed in-house, but also for the applications developed by third-party developers.

Success Metrics

1. Ability to run queries planned in OrgChart 2.0
2. Efficiency over existing REST API calls on complex queries
3. Reduce compute time on the frontend
4. Ability to pushdown filters and pre-processing logic from the front end to the backend. (This rather not loading all data to memory and doing pre-processing, rather pushing down at the reading time and only picking relevant records such that memory usage is optimal. Very useful for large queries)

Testing

TBD

Assumptions

1. GraphQL can provide better performance for complex queries
2. Complex queries will be widely used by the application developers using GIG.