FINERACT-2893: Apply relationshipId when updating a client family member

[rymghosn]

Description

JIRA: FINERACT-2893

Updating a client family member's relationship (PUT /clients/{clientId}/familymembers/{familyMemberId} with a new relationshipId) returned 200 but left the relationship unchanged.

Root cause: ClientFamilyMemberCommandFromApiJsonDeserializer only supports relationshipId, and add-member and create-client-with-family-members read that key. ClientFamilyMembersWritePlatformServiceImpl.updateFamilyMember read the misspelled relationShipId, so the value was ignored. Sending relationShipId instead is rejected as an unsupported parameter, so no payload could change the relationship.

Fix:

• updateFamilyMember reads relationshipId.
• validateForCreate(long, String) and validateForUpdate use the existing RELATIONSHIP_ID constant.
• The misspelled RELATION_SHIP_ID constant is removed.

Tests: new unit test ClientFamilyMembersWritePlatformServiceImplTest.updateFamilyMemberAppliesRelationshipId. It fails on current develop and passes with this change. spotlessJavaCheck passes.

Checklist

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• Add required Swagger annotation and update API documentation at fineract-provider/src/main/resources/static/legacy-docs/apiLive.htm with details of any API changes. No API change: the documented relationshipId parameter now works on update.
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