Move mediaProxy configuration to the top level

This bypasses its weird interactions with ApplyConfig which would
sometimes cause it to not be initialized properly.

config.sample.yaml

@@ -9,16 +9,17 @@ bridge:
   appservicePort: 9555
   # Config for the media proxy
   # required to serve publically accessible URLs to authenticated Matrix media
-  mediaProxy:
-    # To generate a .jwk file:
-    # $ node src/generate-signing-key.js > signingkey.jwk
-    signingKeyPath: "signingkey.jwk"
-    # How long should the generated URLs be valid for
-    ttlSeconds: 3600
-    # The port for the media proxy to listen on
-    bindPort: 11111
-    # The publically accessible URL to the media proxy
-    publicUrl: "https://bifrost.bridge/media"
+
+mediaProxy:
+  # To generate a .jwk file:
+  # $ node src/generate-signing-key.js > signingkey.jwk
+  signingKeyPath: "signingkey.jwk"
+  # How long should the generated URLs be valid for
+  ttlSeconds: 3600
+  # The port for the media proxy to listen on
+  bindPort: 11111
+  # The publically accessible URL to the media proxy
+  publicUrl: "https://bifrost.bridge/media"
 
 roomRules: []
 # - room: "#badroom:example.com"

config/config.schema.yaml

@@ -1,11 +1,11 @@
 "$schema": "http://json-schema.org/draft-07/schema#"
 "$id": "http://matrix.org/bifrost/schema"
 type: object
-required: ["bridge", "datastore", "purple", "portals"]
+required: ["bridge", "mediaProxy", "datastore", "purple", "portals"]
 properties:
     bridge:
         type: object
-        required: ["domain", "homeserverUrl", "userPrefix", "mediaProxy"]
+        required: ["domain", "homeserverUrl", "userPrefix"]
         properties:
           domain:
             type: string
@@ -15,18 +15,18 @@ properties:
             type: string
           appservicePort:
             type: number
-          mediaProxy:
-            type: "object"
-            properties:
-              signingKeyPath:
-                type: "string"
-              ttlSeconds:
-                type: "integer"
-              bindPort:
-                type: "integer"
-              publicUrl:
-                type: "string"
-            required: ["signingKeyPath", "ttlSeconds", "bindPort", "publicUrl"]
+    mediaProxy:
+        type: "object"
+        properties:
+          signingKeyPath:
+            type: "string"
+          ttlSeconds:
+            type: "integer"
+          bindPort:
+            type: "integer"
+          publicUrl:
+            type: "string"
+        required: ["signingKeyPath", "ttlSeconds", "bindPort", "publicUrl"]
     datastore:
         required: ["engine"]
         type: "object"

src/Config.ts

@@ -14,14 +14,10 @@ export class Config {
         homeserverUrl: "",
         userPrefix: "_bifrost_",
         appservicePort: 9555,
-        mediaProxy: {
-            signingKeyPath: "",
-            ttlSeconds: 0,
-            bindPort: 0,
-            publicUrl: ""
-        },
     };
 
+    public readonly mediaProxy: IMediaProxy;
+
     public readonly roomRules: IConfigRoomRule[] = [];
 
     public readonly datastore: IConfigDatastore = {
@@ -109,12 +105,13 @@ export interface IConfigBridge {
     homeserverUrl: string;
     userPrefix: string;
     appservicePort?: number;
-    mediaProxy: {
-        signingKeyPath: string;
-        ttlSeconds: number;
-        bindPort: number;
-        publicUrl: string;
-    },
+}
+
+export interface IMediaProxy {
+    signingKeyPath: string;
+    ttlSeconds: number;
+    bindPort: number;
+    publicUrl: string;
 }
 
 export interface IConfigPurple {

src/Program.ts

@@ -92,7 +92,7 @@ class Program {
     }
 
     private async initialiseMediaProxy(): Promise<MediaProxy> {
-        const config = this.config.bridge.mediaProxy;
+        const config = this.config.mediaProxy;
         const jwk = JSON.parse(fs.readFileSync(config.signingKeyPath, "utf8").toString());
         const signingKey = await webcrypto.subtle.importKey('jwk', jwk, {
             name: 'HMAC',