Pin to specific version (0.0.6) of cisagov/postfix image

[dav3r]

🗣 Description

This PR pins this composition to the current newest version of cisagov/postfix-docker, which is 0.0.6. Previously, we only used cisagov/postfix:latest.

💭 Motivation and context

There are two goals here:

1. Pinning to a specific version moves us toward our goal of more reproducible build processes.
2. We want to pull in the recent improvement from: Add --force-badname flag to useradd command postfix-docker#33.

🧪 Testing

All automated tests pass.

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• All new and existing tests pass.

✅ Pre-merge checklist

• Finalize version.

✅ Post-merge checklist

• Add a tag or create a release.

[coveralls]

Pull Request Test Coverage Report for Build 1742459178

• 0 of 1 (0.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 0.0%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/gophish_init/_version.py	0	1	0.0%

Totals
Change from base Build 1688469728:	0.0%
Covered Lines:	0
Relevant Lines:	45

---

💛 - Coveralls

[mcdonnnj]

Love the strict pinning!

[jsf9k]

1-2-3 🔔 🔔 🔔