Create EDS_API_Test.feature

[Kevsy]

This PR adds a Gherkin feature file with tests for Simple Edge Discovery, as required by the Commonalities API Readiness Checklist

[gunjald]

For the EDSInvalidUEIdentity, can the error code "404 Not Found" be used instead of internal server error ?

[Kevsy]

For the EDSInvalidUEIdentity, can the error code "404 Not Found" be used instead of internal server error ?

RFC9110 defines 404 Not Found as the suitable response code where "[...] the origin server did not find a current representation for the target resource". In this case the User Device Identity is not the target resource, rather it can be considered as an invalid parameter value.

While in some cases an invalid parameter value could be client error in the 4xx range (e.g wrong type), in the case of phone numbers and IP addresses the type syntax can be correct but not recognised by that operator (because of number portability and IP subnet changes). The 500 Internal Server Error allows us to provide details, as per RFC7807 and a common framework to do this is being considered by commonalities

[Kevsy]

@gunjald on second thoughts, to align with Device Identifers and Quality on Demand APIs: I've made the 'EDSInvalidUEIdentity' a 404 as suggested above. It's technically not ideal for the reasons given, but at least it wil be consistent across CAMARA so probably the best option. I've update the .feature file accordingly (same Pull Request)

[Kevsy]

Superseded by #201