Fixing ses email backend

[ignaski]

closes: #16166, #17930
related: #16778, #18200

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[ignaski]

I did some refactoring to bring the repeated code into a single piece of code.
The logic is now that by default send_email will take the sender email and name from configuration. I took the idea from #17930 .In order to keep the previous functionality intact , smtp backend also looks for sender in config smtp section, whereas sendgrid additionaly looks into environment variables.

[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.

[ignaski]

@uranusjr there are a few tests failing which seem to be unrelated to the PR changes, shall I be doing anything regarding it?

[uranusjr]

It seems like the CI failed since it ran out of resource. I think you can disregard those failures.

[uranusjr]

Also see #18200.

[ecerulm]

I would be goog to add a Closes: #17930 to the PR that way it will show on GitHub UI for that issue

[potiuk]

I would be goog to add a Closes: #17930 to the PR that way it will show on GitHub UI for that issue

I linked the issue (GitHub allows to link issue also via UI).

[potiuk]

❤️ it. One step closer to getting saner email configuration for various parts of Airflow.

[ignaski]

@potiuk there is some valuable code in #18200, e.g. extension of config template. I plan to improve this PR by incorporating it here.

[eladkal]

@potiuk should we hold merging this PR as it will cause the Amazon provider to be depended on 2.3.0 ?

[potiuk]

I believe the way it's implemented is fuly backwards compatible and I think we do not particularly depend on 2.3.0 (from what I see we just read conf value which fallbacks to None if not set.

But maybe I overlooked something? @uranusjr @eladkal ? can you spot any incompatibilty ?

[uranusjr]

According to the original issue, the only function this changes in the Amazon provider does not even work right now, so I don't think there's a compatibility issue since there's nothing to be compatible with.