Error when initializing index : "pipeline with id [attachment] does not exist"

Error description

When setting up FullTextSearch on a test installation, with this command ./occ fulltextsearch:index I have the following error coming:

┌─ Errors ────
│ Error:     16/16
│ Index: files:13
│ Exception: Elasticsearch\Common\Exceptions\BadRequest400Exception
│ Message: pipeline with id [attachment] does not exist
│
│
└──

This happens when first initializing the index as mentionned here: https://github.com/nextcloud/fulltextsearch/wiki/Commands#fulltextsearchindex

Workaround

I found a workaround reseting the index with ./occ fulltextsearch:reset and restarting the index with ./occ fulltextsearch:index

This is easy to do on a brand new test env with a very few files, but I guess this can be quite problematic for large instance with many files...

Environment details

Docker, NC22, Elastic Search 7.15.1 with ingest attachment plugin in, see Dockerfile below.

FROM docker.elastic.co/elasticsearch/elasticsearch:7.15.1

RUN bin/elasticsearch-plugin install --batch ingest-attachment

Start by reproducing ./occ fulltextsearch:index with the Elasticsearch 7.15.1 Dockerfile and ingest-attachment plugin configuration shown in the report. Trace the index initialization that produces the missing attachment pipeline error; done means a new index completes without requiring fulltextsearch:reset first.