Using files for secrets

Describe the feature request

Hello, would it be possible to provide the value of secrets through files, in addition to the current environnement variables ?

For example, when using an env variable in config files:

headers:
    Authorization: "Bearer ${MY_API_TOKEN}"

gatus could look

• first at the content of the file whose pathname is in env var $MY_API_TOKEN_FILE if defined (e.g. MY_API_TOKEN_FILE=/run/secrets/my_api_token) (The naming convention xx_FILE is commonly used in other projects, or could be xx__FILE or FILE__xx instead)
• else at the content of env var $MY_API_TOKEN directly, as it is done today.

Such a feature would be compatible with docker secrets, and also would require no change to config files already using env variables.

thanks you very much for gatus!

Why do you personally want this feature to be implemented?

it would be possible to benefit from Docker secrets (and similar mechanisms).

How long have you been using this project?

2 years

Additional information

I have looked at issues #1448 and #1399 , with similar concerns, but different proposals.