Process plugin to convert URL aliases to system URLs

Problem/Motivation

It would be useful to have a process plugin to convert URL aliases to internal URLs, so that they could be further processed using e.g. LinkIt ( ✨ Example migrate process plugin to convert basic "node/123" links to the correct format Needs work ).

Proposed resolution

Add a process plugin that searches looks to see if the URL is in the source database's url_alias table.

Remaining tasks

Provide a process plugin that searches looks to see if the URL is in the source database's url_alias table.

User interface changes

n/a

API changes

TBD

Data model changes

n/a