drf-spectacular in lms

[awais786]

Steps to run this PR.

1. pip install drf-spectacular ( already added into requirements)
2. Generate schema file using this command from shell python manage.py lms spectacular --file schema.yaml
3. In case generate schema with json python manage.py lms spectacular --format openapi-json > schema.json
4. Access the schema via url http://localhost:18000/lms-api/ui/
5. Get this docker file from here
6. Run the commend to generate a client using yaml docker run --rm -v /Users/awais.qureshi/Documents/devstack/todo/schema.yaml:/local/schema.yaml -v /Users/awais.qureshi/Documents/devstack/todo/newclient:/local/out openapitools/openapi-generator-cli generate -i /local/schema.yaml -g python -o /local/out