Allow interceptors to expose arbitrary unstructured metadata

In the short term, this will be used to expose the currently connected
ADB devices for Android ADB interception

Author: pimterry

src/api-server.ts

@@ -127,6 +127,11 @@ const buildResolvers = (
                     reportError(e);
                     return false;
                 }
+            },
+            metadata: (interceptor: Interceptor) => {
+                return interceptor.getMetadata
+                    ? interceptor.getMetadata()
+                    : undefined;
             }
         },
 

src/interceptors/index.ts

@@ -14,6 +14,8 @@ export interface Interceptor {
     id: string;
     version: string;
 
+    getMetadata?(): any;
+
     isActivable(): Promise<boolean>;
     isActive(proxyPort: number): boolean;