* Initial federation sender -> federation API refactoring
* Move base into own package, avoids import cycle
* Fix build errors
* Fix tests
* Add signing key server tables
* Try to fold signing key server into federation API
* Fix dendritejs builds
* Update embedded interfaces
* Fix panic, fix lint error
* Update configs, docker
* Rename some things
* Reuse same keyring on the implementing side
* Fix federation tests, `NewBaseDendrite` can accept freeform options
* Fix build
* Update create_db, configs
* Name tables back
* Don't rename federationsender consumer for now
* Implement /_synapse/admin/v1/register
This is implemented identically to Synapse, so scripts which work
with Synapse should work with Dendrite.
```
Test 27 POST /_synapse/admin/v1/register with shared secret... OK
Test 28 POST /_synapse/admin/v1/register admin with shared secret... OK
Test 29 POST /_synapse/admin/v1/register with shared secret downcases capitals... OK
Test 30 POST /_synapse/admin/v1/register with shared secret disallows symbols... OK
```
Sytest however has `implementation_specific => "synapse"` which stops these
tests from running.
* Add missing muxes to gobind
* Linting
