TRUNK-4860: Add assertion for validation message in ValidateUtilTest

[Jagdish-Singh-Bisht]

Description of what I changed

Added a new unit test to ensure ValidateUtil.validate() exposes the correct validation error message/code when validation fails.

Specifically, I added a test in ValidateUtilTest that:

• Creates an invalid Location object (missing required name)
• Calls ValidateUtil.validate()
• Asserts that a ValidationException is thrown
• Asserts that the underlying Errors object has a field error on "name"
• Verifies that the error code is "error.name"

This improves test coverage for TRUNK-4860, ensuring validators are checked not only for failures but also for correct error messages.

Issue I worked on:

see https://issues.openmrs.org/browse/TRUNK-4860

Checklist: I completed these to help reviewers :

• My IDE is configured to follow the code style
  of this project.
• I have added tests to cover my changes.
• I ran mvn clean package right before creating this pull request and added all formatting changes to my commit.
• All new and existing tests passed.
• My pull request is based on the latest changes of the master branch.