Dataplane Signaling Register endpoint is missing in V4 mgmt openapi schema

# Bug Report

## Describe the Bug

The `PUT /v4/dataplanes` endpoint is missing in the Management API openapi schema under `Dataplane Signaling Registration v4`. As seen here https://eclipse-edc.github.io/Connector/openapi/management-api/ , only the `DELETE` endpoint is visible.

### Expected Behavior

Both the `PUT` and `DELETE` endpoints to be visible as defined here https://github.com/eclipse-edc/Connector/blob/main/data-protocols/data-plane-signaling/data-plane-signaling-core/src/main/java/org/eclipse/edc/signaling/port/api/management/DataPlaneRegistrationApiV4.java#L35

### Observed Behavior

Only the `DELETE` endpoint is shown

## Steps to Reproduce

Steps to reproduce the behavior:

1. Go to https://eclipse-edc.github.io/Connector/openapi/management-api/#/Dataplane%20Signaling%20Registration%20v4
2. Click on `Dataplane Signaling Registration v4` group.
3. Observe that only `DELETE /v4/dataplanes/{dataplaneId}` entry is defined.

## Detailed Description

Might be some openapi spec merging issue as the `Dataplane Selector v4` also defines endpoints under the `/v4/dataplanes` url?

Start with data-protocols/data-plane-signaling/data-plane-signaling-core/src/main/java/org/eclipse/edc/signaling/port/api/management/DataPlaneRegistrationApiV4.java and compare its PUT and DELETE definitions with the generated Management API schema. Then inspect how the Dataplane Signaling Registration v4 and Dataplane Selector v4 endpoints are merged under /v4/dataplanes. Done means the published schema shows both endpoints.

Written by the indexing model from the issue text.