Add secret caching for Airflow CLI

[Birne94]

This PR adds secret caching for the Airflow CLI. Secret caching current only works for the DAG-processing job, but is ignored when parsing the files through the CLI. This currently causes slow response times from the Airflow CLI for DAGs that use top-level variables.

By initializing the cache as part of the CLI startup, we make sure the cache is enabled properly for parsing. If the user did not configure caching explicitly, the added cache initialization is a no-op and the behavior is the same as before.

closes: #37543

I did not add a test case yet because I did not find an existing one for __main__.main() yet. I am open for suggestions on how to properly test the added caching, however since this is a very small change that does not change behavior until explicitly configured we may be good without one.

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[dirrao]

Why can't we use AIRFLOW__SECRETS__USE_CACHE instead of explicitly adding it in CLI?

[Birne94]

The way that secret caching is implemented currently is that the SecretCache class is always used for looking up. If caching is not explicitly enabled, the cache will never be initialized and essentially is a no-op.

The problem is that SecretCache.init() is only called in the dag processing job. This means that if we configure caching and process the DAG there, it will work as expected. However if we load a DAG from any other place (e.g. the CLI), our caching configuration is ignored and cache creation is skipped.

With the change I suggest, the secrets.use_cache option will be honored from the CLI and caching will be enabled as expected.

[uranusjr]

The comment is too vague. What is “some” and why does secret caching affect performance on DAG-parsing?

[Birne94]

I updated the comment, does it make more sense now?

[Taragolis]

Following the discussion into the Dev List and in PR decided to include it only for DagManager processor

• https://lists.apache.org/thread/ppbb87tohos9zs1yv6pf8b2zyq66dmdk
• #30259

By adding this changes into the main cli method it would enable everywhere into airflow.

I would suggest to open a new discussion into the https://airflow.apache.org/community/

For prevent accidentally merge it I mark request changes until proposed it not discussed in more wide audience.

[github-actions]

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