Add service connection and its child subcommands

[khos2ow]

Prerequisites

Put an x into the box(es) that apply:

• This pull request fixes a bug.
• This pull request adds a feature.
• This pull request enhances existing functionality.
• This pull request introduces breaking change.

For more information, see the Contributing Guide.

Description

This PR adds connection commands and all its subcommands, including:

• get
• list

Issues Resolved

List any existing issues this pull request resolves.

Checklist

Put an x into all boxes that apply:

• I have read the Contributing Guidelines.

Tests

• I have added tests to cover my changes.
• All tests pass when I run make test.

Documentation

• My change requires a change to the documentation.
• I have updated the documentation accordingly.

Code Style

• My code follows the code style of this project.
• All checks pass when I run make checkfmt and make lint.