Origin in RideRequest should be required

`Origin` (location of passenger pickup) is defined as an `interface{}` implying that it is optional, but that is not the case.

Locate the RideRequest definition in the Go SDK and inspect how the Origin field is represented and used. Determine the repository's existing approach for required request fields, then update Origin consistently and verify the relevant request-model or API tests; done means pickup requests cannot omit Origin.

Written by the indexing model from the issue text.