Include broken links from content blocks

[brynwhyman]

Overview

Currently this report will not include any external broken links that are included in elemental content blocks. As content blocks become a very popular method of creating content, this report should be tracking this content too.

We've seen a similar enhancement (with an open PR) to the elemental content blocks module to ensure that content is being included in the 'Broken page' and 'Broken links' reports, see silverstripe/silverstripe-elemental#689

ACs

• This looks through every block with a HTML field (including custom blocks)
• The report should continue to reference the page that includes the content block with the broken link. There is no need to reference the block ID
• Running the report should result in broken links being highlighted in the WYSIWYG as 'broken'. Note this is existing behaviour for pages, so the aim is to match this functionality.
• Create a new issue to create a build task to retrospectively find broken links within existing blocks

Notes

• This has been looked at before in Links are checked on $page->Content: won't work with modules like content blocks #37 (see issue for early investigation)

PR's

• NEW Track broken links and files within ElementContent silverstripe-elemental#822
• NEW Track broken links and files within ElementContent silverstripe-elemental#861

[brynwhyman]

I still want to check if there's a UI change to broken links in a WYSIWYG after this report is run (i.e. the link is highlighted) as we may need an AC around this.

[robbieaverill]

Yes, it's supposed to highlight broken links with a red underline

[brynwhyman]

Thanks @robbieaverill. I've added another AC to reflect this:

• Running the report should result in broken links being highlighted in the WYSIWYG as 'broken'. Note this is existing behaviour for pages, so the aim is to match this functionality.

[brynwhyman]

Related/ duplicate: #37

[brynwhyman]

There's a similar issue which we've previously triaged as a bug: silverstripe/silverstripe-elemental#689

[brynwhyman]

Noting that a recent bug was raised for CMS job run for this report. This should be reviewed when this issue is picked up: #69