Add support for spotbugs

[david-waltermire]

User Story:

As a Metaschema Java library developer, I need a static code analyzer that will help me identify bugs in code under development.

Goals:

• Integrate spotbugs into the Maven build pipeline (https://spotbugs.github.io/spotbugs-maven-plugin/usage.html)
• Replace any use of findbugs with spotbugs, which is newer and better supported.

Dependencies:

None.

Acceptance Criteria

• All website and readme documentation affected by the changes in this issue have been updated. Changes to the website can be made in the docs/content directory of your branch.
• A Pull Request (PR) is submitted that fully addresses the goals of this User Story. This issue is referenced in the PR.
• The CI-CD build process runs without any reported errors on the PR. This can be confirmed by reviewing that all checks have passed in the PR.

{The items above are general acceptance criteria for all User Stories. Please describe anything else that must be completed for this issue to be considered resolved.}