Add use_env_var flag to client

[loomlike]

Signed-off-by: Jun Ki Min 42475935+loomlike@users.noreply.github.com

Description

Introduce an option to select between env vars and config yaml file.
Feathr client to use explicitly configured yaml file over environment variable if use_env_var flag is set to False.

The changes are added as the last argument of the existing functions and set default to True (use env variables) so that
existing codes don't break.

Resolves #922

How was this PR tested?

Unit test

Does this PR introduce any user-facing changes?

• No. You can skip the rest of this section.
• Yes. Make sure to clarify your proposed changes.

[Yuqing-cat]

The enhancement looks reasonable. It will be better if we could make _EnvVariableUtil less complex.

[blrchen]

Hello @loomlike seems this doc should get updated as well https://feathr-ai.github.io/feathr/how-to-guides/feathr-configuration-and-env.html#configuration-and-environment-variables-in-feathr

Can I ask is there any use case for introducing this new env? Have this new flag can make configuration more flexible but it introduces complexity on configuration code as well.

[loomlike]

Hello @loomlike seems this doc should get updated as well https://feathr-ai.github.io/feathr/how-to-guides/feathr-configuration-and-env.html#configuration-and-environment-variables-in-feathr

Can I ask is there any use case for introducing this new env? Have this new flag can make configuration more flexible but it introduces complexity on configuration code as well.

The default behavior is to override the config file values (use_env_vars=True) with env variables, so I think we can keep the document as it is.
Usecases are mostly for us to test with different configuration of the client, since if we change the env var of the test machine for each test case, it's not safe (someone can forget to put the original env var back at the end of the test) as well as parallel testing will not work as they'll share the env vars.

[Yuqing-cat]

Looks nice to me! Thanks for the changes.
Please also change the file names envvariableutil.py & test_envvariableutil.py to fit the new class name.

[jainr]

Thanks for making the changes and addressing the comments.