FINERACT-248: Prevent duplicate SMS campaign names

[nickus]

Summary

Add validation to check for duplicate campaign names before creating or updating SMS campaigns. This provides a user-friendly error message instead of relying on database constraint violations.

Changes

• Add existsByCampaignName() and existsByCampaignNameAndIdNot() methods to SmsCampaignRepository
• Validate campaign name uniqueness in create() method before saving
• Validate campaign name uniqueness in update() method when name changes
• Add SmsCampaignNameAlreadyExistsException for clear error messages

Test plan

• Integration tests added for:
  • Creating a campaign with a duplicate name should fail with appropriate error
  • Creating campaigns with unique names should succeed

[galovics]

I think the default isolation level we use is read_committed, meaning only committed things will be revealed by this check. It not guarantees anything.
2 transactions concurrently writing the same campaign name is possible.

If you wanna prevent it, ensure having a unique key on the DB level. This is good for a best-effort check but it's not bullet-proof,.

[nickus]

Actually, there is already a unique key on the DB level. You might see further I catch DataIntegrityViolationException and throw the same exception.

see realCause.getMessage().contains("campaign_name_UNIQUE")

[nickus]

@galovics could you take a fresh look on this please

[adamsaghy]

The mentioned unique constraint is not existing. It's mentioned on the entity, but in reality it does not exist. Please add this missing unique constraint.

[nickus]

Good catch @adamsaghy, you're right — the @UniqueConstraint annotation on the entity was just Hibernate metadata with no actual DB constraint behind it (since DDL auto-generation is disabled). I've added a Liquibase migration to create the campaign_name_UNIQUE constraint on the sms_campaign table.

[adamsaghy]

Kindly review my concerns!