RTD API cleanups: intent to remove RichDocumentFilter and RichDocumentParserObject

[Arnold Hendriks]

We’re looking at removing RichDocumentParserObject and RichDocumentFilter (and basically most of the other lowlevel APIs to RTDs we can find). They were once added to mirror the approach we offered for Word documents, but it’s much more flexible for both the developer and for us internally if you just use DOM APIs to do such changes, if necessary during postprocessing. The DOM coming out of the RTE is extremely predictable already, so why not 

This change will take some time and we’ll first need to add the missing APIs to give you cleaner ways to do whatever you needed these low level APIs for, so we need to hear about what’s needed!

The top use of RichDocumentFilter was to gather the initial paragraphs/text from a document to generate a description or overview, so the first change will be to add an API to grab plaintext directly from a RTD - see here: https://gitlab.com/webhare/platform/-/merge_requests/873

(Repost from forum.webhare.dev)