Lambdas vs Interface for integration points

[abergs]

The library depends on multiple integrations with the RP app.
The RP-app is responsible for:

• Validating that the credentialId is unique to the user (today: isCredentialIdUniqueToUserDelegate with params: byte[], user)
• Validating that the UserHandle owns the CredentialId (today: isUserHandleOwnerOfCredentialId)
• Increasing the stored Counter
• Storing the Public Key + CredentialId returned by the MakeCredential operations

... basically anything that needs storage.

Should the API be based on multiple Func/namedFuncs callbacks or take a implementation of an interface.

I believe an interface will be easier for a user to understand and maintain while the lambdas feel more lightweight, however don't outweigh the maintainability of a interface.

[abergs]

Decided to go for lambdas with typed parameter class, best middleground.