Add Keys and Domain Keys API endpoints

[skupriienko]

Links:

• Jira

Actions:

• Add Keys and Domain Keys API endpoints:

  • Add handle_keys to mailgun.handlers.keys_handler.
  • Add handle_dkimkeys to mailgun.handlers.domains_handler.
  • Add "dkim" key to special cases in the class Config.

• Examples:

  • Add the get_dkim_keys(), post_dkim_keys(), delete_dkim_keys() examples to mailgun/examples/domain_examples.py.
  • Add the get_keys(), post_keys(), delete_key(), regenerate_key() examples to mailgun/examples/keys_examples.py.
  • Update get_own_user_details() by creating client_with_secret_key in mailgun/examples/users_examples.py.

• Docs:

  • Add Keys and Domain Keys sections with examples to README.md.
  • Improve the users' example.
  • Fix markdown structure in README.md.
  • Update environment variables in README.md.
  • Add docstrings to the test class KeysTests & AsyncKeysTests and their methods.
  • Add CONTRIBUTING.md

• Tests:

  • Add dkim keys tests to DomainTests and only test_get_dkim_keys, test_post_dkim_keys_invalid_pem_string to AsyncDomainTests.
  • Add classes KeysTests and AsyncKeysTests to tests/tests.py.
  • Add keys tests to KeysTests and AsyncKeysTests.
  • Move BounceClassificationTests to another place.
  • Replace some pytest's skip marks with xfail.

• CI:

  • Disable codespell pre-commit hook as it lashes with typos.
  • Update pre-commit hooks to the latest versions.

• Linting & Formatting:

  • Run linter & formatters commands.

• Package Management:

  • Update test dependencies: add openssl and pytest-asyncio to environment-dev.yaml and pyproject.toml.
  • Add a constraint py<311 for typing_extensions >=4.7.1 in files environment.yaml, environment-dev.yaml, pyproject.toml, and in mailgun/client.py.
  • Add .server.key to .gitignore.
  • Update the changelog.