Ensure test coverage for each class

[chenrujun]

Parent issue: #23402

Requirements

• Add maven plugin to enforce coverage rate.
• Add more tests if necessary.

Sub tasks:

• Ensure test coverage for Fundamental modules #24405
• Ensure test coverage for Messaging modules @moary #24406
• Ensure test coverage for Storage + Database modules #24407
• Ensure test coverage for Security modules #24408

Steps of using Intellij to get test coverage

Step 1: Run test with coverage

Step 2: Check the coverage result:

Refs: https://www.jetbrains.com/help/idea/running-test-with-coverage.html

[saragluna]

Closed in #26187.