support arrival date & time

Is there any way to specify the time of arrival rather than just the time of departure? Perhaps I should't be abusing this as a more complete version of https://github.com/juliuste/db-hafas-rest/, though...

Start by reading the repository's journey-price request flow and how it uses the DB Sparpreise API. Trace where departure date and time are accepted, then determine how arrival date and time should be represented in the request and results. Done means callers can specify an arrival date and time rather than only a departure time.

Written by the indexing model from the issue text.