Add DOCKER_STEPCA_INIT_PASSWORD_FILE variable for Docker secrets

[francescocapuano]

Add the management of the DOCKER_STEPCA_INIT_PASSWORD_FILE variable. over DOCKER_STEPCA_INIT_PASSWORD. If both are used only DOCKER_STEPCA_INIT_PASSWORD_FILE will be used.

Name of feature:

Add DOCKER_STEPCA_INIT_PASSWORD_FILE variable for Docker secrets

Pain or issue this feature alleviates:

Allow the possibility to use Docker Secrets for step-ca init password

Why is this important to the project (if not answered above):

This allow to use a predefined password with having to use enviromental variables

Is there documentation on how to use this feature? If so, where?

I can do it, but I don't know where in this repo

In what environments or workflows is this feature supported?

Docker

In what environments or workflows is this feature explicitly NOT supported (if any)?

Supporting links/other PRs/issues:

💔Thank you!

[CLAassistant]

All committers have signed the CLA.

[tashian]

Thanks @francescocapuano for this contribution.
I can update the docs on Docker Hub to reflect this variable.

[hslatman]

Thank you, @francescocapuano 😄