Refactor Getting started docs

[kondratevdev]

I have made things!

Checklist

• I have double checked that there are no unrelated changes in this pull request (old patches, accidental config files, etc)
• I have created at least one test case for the changes I have made
• I have updated the documentation for the changes I have made

Related issues

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (93f3387) to head (7471670).

Additional details and impacted files

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##            master      #665   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files          285       285           
  Lines        11862     11862           
  Branches       403       403           
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  Hits         11862     11862           

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[sobolevn]

Do we really need all imports here? Maybe we can just create another file with the minimal setup?

from dmr import Body, Controller, Headers
from dmr.plugins.msgspec import MsgspecSerializer

are not really required.

[sobolevn]

I don't like that the swagger part is gone, it should be in the first example.

Also, this part is also gone:

if __name__ == '__main__':
    # Use `python THIS_FILE_NAME.py runserver` to run the example.
    # Then visit `http://localhost:8000/docs/swagger` to view the docs.
    execute_from_command_line(sys.argv)

We need to get the working app by the end of this guide. And now there's nothing we can actually run and test.

Things to fix:

1. Swagger
2. manage.py
3. settings.configure