(refactor) Replace usages of `/ws/rest/v1/` with restBaseUrl

[jwnasambu]

Requirements

• [x] This PR has a title that briefly describes the work done including the ticket number. If there is a ticket, make sure your PR title includes a conventional commit label. See existing PR titles for inspiration.
• [ ] My work conforms to the OpenMRS 3.0 Styleguide and design documentation.
• [ ] My work includes tests or is validated by existing tests.

Summary

Change all instances of the hard-coded API base URL '/ws/rest/v1/' to use the restBaseUrl variable instead. To enhances maintainability and flexibility of the API base URL configuration.

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Related Issue

https://openmrs.atlassian.net/browse/O3-2815

Other

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Thanks, @jwnasambu!