Field possibly erroneously set as `Schema.RequiredMode.REQUIRED`

### Current Behavior

https://github.com/DependencyTrack/dependency-track/blob/626a0cbf1525fe75d1e00ef3423086173ce58963/src/main/java/org/dependencytrack/model/RepositoryMetaComponent.java#L84-L90

Comment says it's optional and from a quick search through the code base it appears to indeed be conditionally set, not set at all, etc.

This may cause issues for generated OpenAPI clients which assume that the field is always set.

### Steps to Reproduce

An API call to `/v1/repository/latest` may return data such as:
```json
{
"repositoryType": "NPM",
"name": "buffer",
"latestVersion": "6.0.3",
"lastCheck": 1775555220982
}
```
in which `published` is absent.

### Expected Behavior

Either `published` to always have some value (`0`?) or, for it not be set as required.

### Dependency-Track Version

4.13.3

### Dependency-Track Distribution

Container Image

### Database Server

N/A

### Database Server Version

_No response_

### Browser

N/A

### Checklist

- [x] I have read and understand the [contributing guidelines](https://github.com/DependencyTrack/dependency-track/blob/master/CONTRIBUTING.md#filing-issues)
- [x] I have checked the [existing issues](https://github.com/DependencyTrack/dependency-track/issues) for whether this defect was already reported