endpoint to create a new datastream

we need an endpoint to create a new datastream. This is a requirement from the qaqc dataproduct creation.

we can reuse this [1] function and simply expose name as a parameter name:str|None=None. if None we use the default naming schema otherwise we use the given name.

[1] https://codebase.helmholtz.cloud/ufz-tsm/timeio-db-api/-/blob/main/app/crud.py?ref_type=heads#L58