Complement runner configures the media worker as `synapse.app.generic_worker` instead of `synapse.app.media_repository`, which looks like it shouldn't work but apparently does

[reivilibre]

https://element-hq.github.io/synapse/latest/workers.html#synapseappmedia_repository

This seems to be the only place where the app name matters for the media repo:

synapse/synapse/config/repository.py

Line 129 in f95cfd8

and config.get("worker_app") != "synapse.app.media_repository"

but crucially it does seem to matter! But the Complement tests are passing...?

#16803 (comment)

[erikjohnston]

Huh, yeah. Looks like either the app can be synapse.app.media_repository OR enable_media_repo can be set to True.

Given we want to move everything to a single app (generic worker) and instead use config options, this is probably correct. We should double check / test this behaviour and then document it.