Allow file paths to provide URI lists

[steveworley]

Description The crawler addition adds the ability to scan a website for paths the output of this command creates a new file. The current process expects us to copy the URIs output in the file to the content configuration file, this quickly becomes unwieldy it would be cleaner to add the file generated by the crawler and have the configuration parser pull the URI list from file.

Proposed solution

• Update the migrate command so that the configuration for URL list can be a file path or URI (path)

If a file is used it might be a good approach to lazy load the URIs so we don't need to load the entire file into memory to process.

Additional context

urls:
  - file://path/to/uri-list.json
  - /one-off-path.html

[stooit]

This is complete, possible by providing urls_file which points to one or multiple outputs from the crawler.

Docs: https://salsadigitalauorg.github.io/merlin-framework/docs/url-options#urls-in-separate-files