(fix) O3-5173: Validate existence of an active visit for a patient before allowing bill creation

[ELVIS-KATO]

Requirements

• This PR has a title that briefly describes the work done including a conventional commit type prefix and a Jira ticket number if applicable. See existing PR titles for inspiration.
• My work is based on designs, which are linked or shown either in the Jira ticket or the description below.
• My work includes tests or is validated by existing tests.

Summary

I have added a validation functionality to prevent bill creation for patients without active visits.
This mainly checks whether the patient has an active visit, and if they do not have one, it shows a validation error "Patient must have an active visit". I have provided a short video to explain better.

Screenshots

A short video below:

validation.mp4

Related Issue

https://openmrs.atlassian.net/issues?filter=-4&selectedIssue=O3-5173

Other

@VeronicaMuthee @denniskigen

[denniskigen]

So, as far as I'm aware, the issue here is that the Bill data model in the backend has no knowledge of a Visit. If we want to create a coupling between the two, I imagine we'd need to it in the backend first. Right, @ibacher?

[ibacher]

Yes, but also, it's not clear to me that this is work to be done: https://openmrs.slack.com/archives/C06D4666UQ7/p1762876063229869?thread_ts=1762872479.872659&cid=C06D4666UQ7

[denniskigen]

Set to draft because this should evolve into a Talk post or something similar.