What about Kubernetes Secrets vs. environment variables support in Craft

Hi guys,

I want to startup a discussion about Kubernetes Secrets. Not that this is a part of the Craft CMS support, but it has something to do with environment variables, which Craft supports.

Maybe you know, maybe you don't... But Secrets in Kubernetes are used to store credentials in. Those secrets are basically put back into containers as files, mounted typically on something like /run/secrets/ or whatever.
For now I have to do put them in a configuration file, since I have to read the contents of these files like file_get_contents(getenv('MY_ENV_VAR_AS_SECRET')).
This way I can't use the environment variables directly in the CP env-vars-support fields like email settings or site settings etc.

For example; In Symfony you can use these kind of secrets like parameters defined as %env(file:MY_ENV_VAR_AS_SECRET)%. The "file" keyword is being parsed as a file_get_contents() would do. Maybe this is something Craft can support too. This makes working with Secrets in new environment infrastructures (like Kubernetes) and Craft even more powerful.

I hope you see the value of this and I would like to talk about this kinda feature.

Additional info

• Craft version: 3.4.15
• PHP version: 7.4.4

Start by reviewing Craft's existing environment-variable support and the Kubernetes Secrets workflow described in the issue. Determine how mounted secret files should be referenced in CP environment-variable fields, then define and test the proposed file-based expansion.