feat(obligation_classifications): Add admin apis for creating, listing and deleting obligation classifications

[deo002]

Changes

• Added admin APIs to create, delete and get a list of obligation classifications.
• POST /obligations/classifications: Creates a new obligation classification if not already present. It must be non-empty and uppercase. If the obligation classifications to be created is already in db with 'active' flag set to false, it is changed to true.
• DELETE /obligation/classifications/{classification}: The {classification} is soft-deleted if it exists in db, has 'active' flag set to true and no obligation references it.
• GET /obligations/classifications: Fetches a list of all obligation classifications. Flag 'active' can be set to false to fetch the inactive classifications. During obligation creation and updation, associate them with only active obligations.

Submitter Checklist

• [ ] Includes tests (if there is a feature changed/added)
• [X] Includes docs ( if changes are user facing)
• [X] I have tested my changes locally.

References

[GMishx]

The current JSON response is not in camelCase as with other endpoints. But for POST it is in camelCase.