Integrate Django REST Framework.

[furioness]

Make basic functionality available via REST APIs, such as:

• create schema;
• update schema (full replace - POST);
• delete schema;
• call dataset generation;
• get datasets.

And add a basic Postman collection.

[furioness]

Possible REST endpoints:
schemas/ - get/post
schemas/<schema_id> - get/put/delete. Columns are only to be replaced entirely here, no column_id is accepted.

schemas/<schema_id>/columns - get/post
schemas/<schema_id>/columns/<col_id> - put/delete
schemas/<schema_id>/columns/add - post

schemas/<schema_id>/datasets - get
schemas/<schema_id>/datasets/<dataset_id> - get
schemas/<schema_id>/datasets/generate - post

Plus something for authentication.