chore: use NATIONAL_ID so it can be searched with

[naftis]

Instead of the BIRTH_CONFIGURABLE_IDENTIFIER, lets use NATIONAL_ID so it supports searching by default. IMO this is not ideal as we need custom mapping country-config code, but Events V2 should address this via allowing configuring what can be searched with.

[github-actions]

Oops! Looks like you forgot to update the changelog. When updating CHANGELOG.md, please consider the following:

• Changelog is read by country implementors who might not always be familiar with all technical details of OpenCRVS. Keep language high-level, user friendly and avoid technical references to internals.
• Answer "What's new?", "Why was the change made?" and "Why should I care?" for each change.
• If it's a breaking change, include a migration guide answering "What do I need to do to upgrade?".

[tahmidrahman-dsi]

Nice one