Correctly handle multiple '=' in LocalFileSystem secrets.

[kadai0308]

Related issue: #21625

If there is another '=' in the conn string in the env file, it will been splited into 3 sub-string which is not expected( We expect it only been splited into 2 sub-string, key and value ).

For example,

MY_CONN_ID=my-conn-type://my-login:my-pa%2Fssword@my-host:5432/my-schema?param1=val1&param2=val2

it will been splited into:

['MY_CONN_ID', 'my-conn-type://my-login:my-pa%2Fssword@my-host:5432/my-schema?param1', 'val1&param2=val2']

and it will cause ValueError: too many values to unpack (expected 2) laster at line 87 .

key, value = var_parts

It can been fixed by correct the maxsplit to 1 of line split use partition instead in _parse_env_file function in LocalFileSystem secrets.

Python docs: https://docs.python.org/3.11/library/stdtypes.html?#str.split

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[boring-cyborg]

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[mik-laj]

Can you add tests to avoid regression?

[kadai0308]

Can you add tests to avoid regression?

Sure

[github-actions]

The PR most likely needs to run full matrix of tests because it modifies parts of the core of Airflow. However, committers might decide to merge it quickly and take the risk. If they don't merge it quickly - please rebase it to the latest main at your convenience, or amend the last commit of the PR, and push it with --force-with-lease.

[boring-cyborg]

Awesome work, congrats on your first merged pull request!