Docker secrets as templates

[hazzuk]

Description

Docker secrets are now defined using templates (instead of convoluted defaults variables).

See hazzuk/karo-custom#23 for a reference implementation.

Changes

• The 'deploy' tasks have been moved to up.yml. Simplifying the role, and allowing for secrets to be templated.
• New karo_compose_secrets_path variable, set dynamically at runtime per stack.
• Secrets created using templates, and each end of file newline is automatically removed.

Notes

Secrets as templates have some large advantages:

• The compose. dictionary variable can now be used to reference a stack variable.
• Avoids the need for long-winded variable definitions.
• Much more visually representative of how secrets are passed to compose stacks.
• Secrets can now be left undefined, and instead rely on the stack defaults variables.

Checklist

• Written documentation
• [n/a] Linked relevant issues

[hazzuk]

Secrets documentation changes complete: https://docs.karolabs.dev/dev/compose/secrets/

@mosslocker changes have been made since yesterday, which should further help to clarify how secrets work.