Acceptable

* Assorted fixes and improvements in generated OpenAPI specs
* Extend generated OpenAPI specs with support for query params (fixes 149)
* Code cleanup with `flake8`
* Reformat code with `isort`

* Add new Django command ``openapi``. Generates ``openapi.yaml``
* Update format when a single endpoint supports multiple methods.
* 📢 Please note! operationId now includes both the endpoint name and the method. For example, ``validation-get`` instead of ``validation``. This allows multiple methods on a single endpoint, such as ``validation-post`` and ``validation-get``.

* Sort tags to stabilise YAML order
* Fix OpenAPI spec output when a single endpoint supports multiple methods

* Codebase is blackened
* ``lint --create`` will also generate a valid but incomplete ``openapi.yaml``:

* includes paths, methods, path parameters, request schema, response schema
* operations include operationId, description and summary (if found)
* group names are included as tags
* version is given as 0.0.V where V is the version number

* Drop support for Python < 3.8, so only Ubuntu 20.04 LTS and 22.04 LTS.

* Improvements to the includable make file.