NEW Migrate code from other modules

[emteknetnz]

Issue silverstripe/.github#342

Separate commits so please do no squash merge

Code copied from silverstripe/securityreport has had any code relating to subsites removed

Any code that was relating to silverstripe/subsites or silverstripe/contentreport has been removed as those module will not be commercially supported going forward

[GuySartorelli]

The external broken links report doesn't work. I click "create new report" and it does nothing. Looking at the dev console there are some missing files. I think you're missing the expose entry for client/dist in composer.json

The folder structure between the newly copied code is also not standardised. e.g. ExternalLinks has a Reports subfolder, but the other two don't. Please make the folder structure uniform across all three feature dirs.

[emteknetnz]

The external broken links report doesn't work. I click "create new report" and it does nothing. Looking at the dev console there are some missing files. I think you're missing the expose entry for client/dist in composer.json

Works fine on my local

The folder structure between the newly copied code is also not standardised. e.g. ExternalLinks has a Reports subfolder, but the other two don't. Please make the folder structure uniform across all three feature dirs.

Have updated

[GuySartorelli]

External broken links report still doesn't work for me. I'm just using installer (not sink) and pulling in only this PR since it shouldn't rely on any of the other changes from what I can tell.

Ignore me, it works fine, I just was pulling it in wrong

[emteknetnz]

Have moved docs for external links + site wide content report do docs/en/index.md

[GuySartorelli]

LGTM