Automate API documentation generation with GitHub Actions

[varshadr]

Problem

Currently, the API documentation is not generated automatically for pull requests. Therefore, API documentation may not be up-to-date

Proposed solution

Add a GitHub Actions workflow to generate the API documentation for pull requests to the develop branch. The workflow should build a Docker image, run the ./manage.py spectacular --color --file schema.yml
command to generate the API documentation, and commit the schema file to the branch.