Server key component (#1050)

* Server key API (works for monolith but not for polylith yet)

* Re-enable caching on server key API component

* Groundwork for HTTP APIs for server key API

* Hopefully implement HTTP for server key API

* Simplify public key request marshalling from map keys

* Update gomatrixserverlib

* go mod tidy

* Common -> internal

* remove keyring.go

* Update Docker Hub for server key API

* YAML is funny about indentation

* Wire in new server key API into hybrid monolith mode

* Create maps

* Route server key API endpoints on internal API mux

* Fix server key API URLs

* Add fetcher behaviour into server key API implementation

* Return error if we failed to fetch some keys

* Return results anyway

* Move things about a bit

* Remove unused code

* Fix comments, don't use federation sender URL in polylith mode

* Add server_key_api to sample config

* Review comments

* HTTP API to cache keys that have been requested

* Overwrite server_key_api listen in monolith hybrid mode

serverkeyapi/api/http.go

@@ -0,0 +1,57 @@
+package api
+
+import (
+	"context"
+
+	commonHTTP "github.com/matrix-org/dendrite/internal/http"
+	"github.com/matrix-org/gomatrixserverlib"
+
+	"github.com/opentracing/opentracing-go"
+)
+
+const (
+	// ServerKeyInputPublicKeyPath is the HTTP path for the InputPublicKeys API.
+	ServerKeyInputPublicKeyPath = "/serverkeyapi/inputPublicKey"
+
+	// ServerKeyQueryPublicKeyPath is the HTTP path for the QueryPublicKeys API.
+	ServerKeyQueryPublicKeyPath = "/serverkeyapi/queryPublicKey"
+)
+
+type InputPublicKeysRequest struct {
+	Keys map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult `json:"keys"`
+}
+
+type InputPublicKeysResponse struct {
+}
+
+func (h *httpServerKeyInternalAPI) InputPublicKeys(
+	ctx context.Context,
+	request *InputPublicKeysRequest,
+	response *InputPublicKeysResponse,
+) error {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "InputPublicKey")
+	defer span.Finish()
+
+	apiURL := h.serverKeyAPIURL + ServerKeyInputPublicKeyPath
+	return commonHTTP.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+}
+
+type QueryPublicKeysRequest struct {
+	Requests map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.Timestamp `json:"requests"`
+}
+
+type QueryPublicKeysResponse struct {
+	Results map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult `json:"results"`
+}
+
+func (h *httpServerKeyInternalAPI) QueryPublicKeys(
+	ctx context.Context,
+	request *QueryPublicKeysRequest,
+	response *QueryPublicKeysResponse,
+) error {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "QueryPublicKey")
+	defer span.Finish()
+
+	apiURL := h.serverKeyAPIURL + ServerKeyQueryPublicKeyPath
+	return commonHTTP.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+}