Rename LDP `DEFAULT_STREAM_ID` setting to `STREAM_ID`

[jmaupetit]

Bug Report

Expected behavior/code

When selecting the ldp backend from the CLI, we expect to be able to set the stream we are targeting with an explicit option name.

Actual Behavior

The --ldp-stream-id does not exist. I suppose Ralph expects this option to be set via the --ldp-default-stream-id option.

Steps to Reproduce

$ ralph list -b ldp --help

Environment

• Ralph version: 4.1.0
• Platform: GNU/Linux

Possible Solution
Rename the LDPDataBackendSettings.DEFAULT_STREAM_ID setting to LDPDataBackendSettings.STREAM_ID

[jmaupetit]

After IRL discussions with @wilbrdt, the stream ID can also be set via the --target option, which is not explicit. There's room for improvement here.