Mautrix

* *(appservice)* Added try blocks around [MSC3202] handler functions to log
errors instead of failing the entire transaction. This matches the behavior
of errors in normal appservice event handlers.

* *(client.api)* Added option to pass custom data to `/createRoom` to enable
using custom fields and testing MSCs without changing the library.
* *(client.api)* Updated [MSC3870] support to send file name in upload complete
call.
* *(types)* Changed `set_edit` to clear reply metadata as edits can't change
the reply status.
* *(util.formatter)* Fixed edge case causing negative entity lengths when
splitting entity strings.

* *(util.async_db)* Fixed mistake in default no-op database error handler
causing the wrong exception to be raised.
* *(crypto.store.asyncpg)* Updated `put_group_session` to catch unique key
errors and log instead of raising.
* *(client.api)* Updated [MSC3870] support to catch and retry on all
connection errors instead of only non-200 status codes when uploading.

* *(crypto)* Fixed handling key requests when using appservice-mode (MSC2409)
encryption.
* *(appservice)* Added workaround for dumb servers that send `"unsigned": null`
in events.

* *(crypto)* Fixed error sharing megolm session if a single recipient device
has ran out of one-time keys.

* **Breaking change *(util.async_db)*** Added checks to prevent calling
`.start()` on a database multiple times.
* *(appservice)* Fixed [MSC2409] support to read to-device events from the
correct field.
* *(appservice)* Added support for automatically calling functions when a
transaction contains [MSC2409] to-device events or [MSC3202] encryption data.
* *(bridge)* Added option to use [MSC2409] and [MSC3202] for end-to-bridge
encryption. However, this may not work with the Synapse implementation as it
hasn't been tested yet.
* *(bridge)* Replaced `homeserver` -> `asmux` flag with more generic `software`
field.
* *(bridge)* Added support for overriding parts of config with environment
variables.
* If the value starts with `json::`, it'll be parsed as JSON instead of using
as a raw string.
* *(client.api)* Added support for [MSC3870] for both uploading and downloading
media.
* *(types)* Added `knock_restricted` join rule to `JoinRule` enum.
* *(crypto)* Added warning logs if claiming one-time keys for other users fails.

[MSC3870]: https://github.com/matrix-org/matrix-spec-proposals/pull/3870