also add tests

Fix noisy "twisted.internet.task.TaskStopped" errors in logs

Treat an invalid .well-known the same as an absent one

Fixes #4003

... basically, carry on and fall back to SRV etc.

Caching for invalid .well-knowns

Update federation routing logic to check .well-known before SRV

Also add a Measure block around the .well-known fetch

Copy over non-federatable trait on room upgrade

I can't figure out what's going on with #4422 and #4436; perhaps this will help.

* Reject large transactions on federation

* Add changelog

* lint

* Simplify large transaction handling

* update debian installation instructions

* docs PR is docs

* by default include m.room.encryption on invites

* fix constant

* changelog

Fix remote invite rejections not coming down sync

remove trailing ,