Make ImapHook mail body encoding configurable

[prutheus]

---

Airflow IMAP Hook only decodes with UTF-8 I use the airflow imap hook, which internally only parses mail body with UTF-8 encoding. I have a mail with some German characters such as ü in text, so what is a way to be able to parse that mails as well?

69        with ImapHook(imap_conn_id="imap") as conn:
70            attachments = conn.retrieve_mail_attachments(
71                name="(.*).PDF",
72                check_regex=True,
73                mail_folder="INBOX",
74                mail_filter="(UNSEEN)",
75                not_found_mode="warn"
76            )

Fails with:

[...]
    mail_body_str = mail_body.decode("utf-8")  # type: ignore
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xfc in position 8269: invalid start byte

https://airflow.apache.org/docs/apache-airflow-providers-imap/stable/_modules/airflow/providers/imap/hooks/imap.html#ImapHook.retrieve_mail_attachments

    def _fetch_mail_body(self, mail_id: str) -> str:
        if not self.mail_client:
            raise Exception("The 'mail_client' should be initialized before!")
        _, data = self.mail_client.fetch(mail_id, "(RFC822)")
        mail_body = data[0][1]  # type: ignore # The mail body is always in this specific location
        mail_body_str = mail_body.decode("utf-8")  # type: ignore
        return mail_body_str

This PR makes the encoding configurable.

^ Add meaningful description above Read the Pull Request Guidelines for more information. In case of fundamental code changes, an Airflow Improvement Proposal (AIP) is needed. In case of a new dependency, check compliance with the ASF 3rd Party License Policy. In case of backwards incompatible changes please leave a note in a newsfragment file, named {pr_number}.significant.rst or {issue_number}.significant.rst, in newsfragments.

[boring-cyborg[bot]]

Congratulations on your first Pull Request and welcome to the Apache Airflow community! If you have any issues or are unsure about any anything please check our Contributors' Guide (https://github.com/apache/airflow/blob/main/contributing-docs/README.rst) Here are some useful points:

• Pay attention to the quality of your code (ruff, mypy and type annotations). Our pre-commits will help you with that.
• In case of a new feature add useful documentation (in docstrings or in docs/ directory). Adding a new operator? Check this short guide Consider adding an example DAG that shows how users should use it.
• Consider using Breeze environment for testing locally, it's a heavy docker but it ships with a working Airflow and a lot of integrations.
• Be patient and persistent. It might take some time to get a review or get the final approval from Committers.
• Please follow ASF Code of Conduct for all communication including (but not limited to) comments on Pull Requests, Mailing list and Slack.
• Be sure to read the Airflow Coding style.
• Always keep your Pull Requests rebased, otherwise your build might fail due to changes not related to your commits. Apache Airflow is a community-driven project and together we are making it better 🚀. In case of doubts contact the developers at: Mailing List: [email protected] Slack: https://s.apache.org/airflow-slack

[potiuk]

Usually we expect unit tests modified whenever any new functionality is added. Can you add one please? It seems imap has quite comprehensive set of tests and it should be possible to add some more similar tests with the new flag covered.

[prutheus]

@potiuk @dirrao I have added some tests.

[eladkal]

Tests are failing. Can you look into it?

[github-actions[bot]]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 5 days if no further activity occurs. Thank you for your contributions.