Don't add rejected events if we've seen them befrore. Add some comments to explain what the code is doing mechanically

Create index on user_ips in the background

Slightly saner logging for unittests

1. Give the handler used for logging in unit tests a formatter, so that the
output is slightly more meaningful

2. Log some synapse.storage stuff, because it's useful.

A bit of a cleanup for background_updates, and make sure that the real
background updates have run before we start the unit tests, so that they don't
interfere with the tests.

user_ips is kinda big, so really we want to add the index in the background
once we're running. Replace the schema delta with one which will do that.

I've done this in a way that's reasonably easy to reuse as there a few other
indexes I need, and I don't suppose they will be the last.

make /devices return a list

Turns out I specced this to return a list of devices rather than a dict of them

Implement GET /device/{deviceId}

Preserve device_id from first call to /register

GET /devices endpoint

device_id may only be passed in the first call to /register, so make sure we
fish it out of the register `params` rather than the body of the final call.

(pick up PR #938 in the hope of fixing the UTs)

Record device_id in client_ips

Register a device_id in the /v2/register flow.

implement a GET /devices endpoint which lists all of the user's devices.

It also returns the last IP where we saw that device, so there is some dancing
to fish that out of the user_ips table.

Record the device_id when we add a client ip; it's somewhat redundant as we
could get it via the access_token, but it will make querying rather easier.

Fix some more comments on some things

This doesn't cover *all* of the registration flows, but it does cover the most
common ones: in particular: shared_secret registration, appservice
registration, and normal user/pass registration.

Pull device_id from the registration parameters. Register the device in the
devices table. Associate the device with the returned access and refresh
tokens. Profit.

Add metrics for psutil derived memory usage

Don't notify pusher pool for backfilled events

Type annotations

Further registration refactoring