Merge federationapi, federationsender, signingkeyserver components (#2055)

* 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

setup/base/federation.go

@@ -0,0 +1,32 @@
+package base
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/http"
+)
+
+// noOpHTTPTransport is used to disable federation.
+var noOpHTTPTransport = &http.Transport{
+	Dial: func(_, _ string) (net.Conn, error) {
+		return nil, fmt.Errorf("federation prohibited by configuration")
+	},
+	DialContext: func(_ context.Context, _, _ string) (net.Conn, error) {
+		return nil, fmt.Errorf("federation prohibited by configuration")
+	},
+	DialTLS: func(_, _ string) (net.Conn, error) {
+		return nil, fmt.Errorf("federation prohibited by configuration")
+	},
+}
+
+func init() {
+	noOpHTTPTransport.RegisterProtocol("matrix", &noOpHTTPRoundTripper{})
+}
+
+type noOpHTTPRoundTripper struct {
+}
+
+func (y *noOpHTTPRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
+	return nil, fmt.Errorf("federation prohibited by configuration")
+}