Add PostgreSQL container

[smilerz]

Pull request

Purpose
Added PostgreSQL app container

Open Questions and Pre-Merge TODOs
Check all boxes as they are completed

• Created all app specific yml files.
• Created postgres documentation file.
• Add link to documentation in mkdocs.yml.
• Tested adding and removing app with command line.
• Tested adding and removing app with GUI.

Learning
Describe the research stage
Links to blog posts, patterns, libraries or addons used to solve this problem

Requirements
Check all boxes as they are completed

• These changes meet the standards for contributing.
• I have read the code of conduct.