Add via parameter on join room requests as per MSC4156 #13

Job	Run time
Unit tests	2m 58s
Linting	1m 4s
Build for Windows (windows, amd64)	1m 3s
Build for Linux (linux, amd64)	59s
WASM build test	0s
Build for Linux (linux, 386)	1m 16s
Initial tests passed	2s
Upgrade tests from HEAD-2	30s
Sytest (SQLite native)	6m 9s
Integration tests	5m 36s
Sytest (SQLite Cgo)	6m 10s
Complement (SQLite native)	4m 12s
Upgrade tests	29s
Sytest (PostgreSQL)	7m 46s
Complement (SQLite Cgo)	4m 51s
Complement (PostgreSQL)	9m 12s
Integration tests passed	4s
Update Docker images	0s
	52m 21s

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