ExternalRefType entry for EU AI Act Union-wide unique single identification

[bact]

Upon the registration of high-risk AI systems to the "EU database for high-risk AI systems listed in Annex III" in relation to testing in real world conditions, a "Union-wide unique single identification number of the testing in real world conditions" Article 60 (4)(c); Article 61 (e); Annex IX (1)) will be submitted.

We may consider to have it as a new type in ExternalRefType.

Possible names: eudb, euaidb, euDatabaseTestId, euDatabaseTest

It is possible that the EU AI Office may issue the schema/string pattern for the identification number in the future.