Issue 1818: Improve our checksum support for Maven metadata

[sainalshah]

Pull Request Description

This pull request closes strongbox/strongbox#1818

Acceptance Test

• Building the code with ng build still works.
• Building the code with ng test still works.
• Building the code with ng e2e still works.

Questions

• Does this pull request break backward compatibility?

  • Yes
  • No

• Does this pull request require other pull requests to be merged first?

  • Yes, please see #...
  • No

• Does this require an update of the documentation?

  • Yes, please see strongbox/strongbox-docs#{PR_NUMBER}
  • No

Code Review And Pre-Merge Checklist

• My code follows the coding convention of this project.
• I have performed a self-review of my own code.
• I have commented my code in hard-to-understand areas.
• My changes generate no new warnings.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.