Dockerfile improvements

[pataquets]

• Add ENTRYPOINT, so now it's just docker run -it cloudinary [command].
• Bump Python version to (almost) latest 3.12. Note: 3.13.0 was released just last week (as of 15-Oct).
• Add a PYHTON_VERSION build ARG to use a specific Python base image version to build from.

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Brief Summary of Changes

What does this PR address?

• GitHub issue (Docker image containing cloudinary-cli #25, follow-up to Docker file added #96)
• Refactoring
• New feature
• Bug fix
• Adds more tests

Are tests included?

• Yes
• No

Reviewer, please note:

Follow-up of #96.
Notice that current Dockerfile is not a source build, but a download-from-pypi-and-install build, and it is not pinned to any version. It'll suffice for a "Just Build ™️" from repo one liner to hit the road ASAP:

$ # Build image straight from source Github repo URL (no clone needed)
$ docker build -t cloudinary https://github.com/cloudinary/cloudinary-cli.git#main
$ # Profit!
$ docker run --rm -it cloudinary config

But it won't work for local development workflow.

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I ran the full test suite before pushing the changes and all the tests pass.

[const-cloudinary]

@pataquets those are great improvements!

Thank you for contribution!

[colbyfayock]

@pataquets thanks for your contribution. this PR is eligible for free Cloudinary Hackatoberfest swag. Please send me an email at [email protected] with your name, GitHub username, and a link to the PR where I'll send further instructions.

Happy Hacktoberfest!