Adding the "existing" side of a self relationship breaks the relationship

Parent Issue

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Problem Statement

When a user adds a relationship field to match an existing self-related field in the same content type, the relationship record in the database is broken, and a duplicate relationship is created. This problem generates inconsistent results in the data, showing duplicate records and sometimes linking related content to the wrong relationship field.

Steps to Reproduce

1. Create a content type
2. Add a relationship field to itself
3. Add another relationship field, but this time, choose "Existing" and select the field created in 2

If you go to the database and query the relationship table, you will notice that 2 relationships were created instead of 1. Relating a self-relationship's "existing" side should work the same way it does for non-self-related fields. The relationship record in the database must be updated instead of creating a second one

Acceptance Criteria

Adding the "existing" side of a self-relationship should not create duplicates in the relationship table. The field parent_relation_name in the existing relationship should be updated instead of creating a new relationship record.

Important note: As part of the fix, we have to make sure that pushing a content type (using PP or dotCLI) with a self-related field is working as expected, especially after adding an "existing" side of the relationship (which would require an additional push to update)

dotCMS Version

25.03.04

Proposed Objective

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Proposed Priority

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External Links... Slack Conversations, Support Tickets, Figma Designs, etc.

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Assumptions & Initiation Needs

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Quality Assurance Notes & Workarounds

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Sub-Tasks & Estimates

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Parent: #31604

Begin by reproducing the self-related content type flow and inspecting the relationship table after selecting the existing field. Trace the content-type push paths for PP and dotCLI, including the additional push required after adding the existing side. Done means the existing relationship is updated through both flows without duplicate records or incorrect field links.