DecodeCredentials takes the request body in JSON format and decodes it into the Credentials struct.

DecodeUser takes the request body in JSON format and decodes it into the User struct.

MapCredentialsToAPI takes a domain object of credentials and maps it to the API model.

MapCredentialsToDomain takes an API object of credentials and maps it to the domain model.

MapUserToAPI takes a domain object of User and maps it to the API model.

MapUserToDomain takes an API object of User and maps it to the domain model.

Credentials defines the necessary parameters for a user to sign in and sign up.

User defienes the user info that will be exposed through the API.