Delete Segment Plugin: Support name extraction from payload

[alirasoli]

Hi,

I am using the Add Segment plugin to dynamically segment users via API calls. I also want to remove these segments later using the Delete Segment plugin. However, the Delete Segment plugin currently only accepts a static segment name, which makes it impossible to delete dynamically created segments via API.

I plan to submit a pull request to update this plugin so it can extract the segment name from the payload similar to how the Add Segment plugin works.