Move reset() to a void return type in the internal remote API

This replaces an unchecked (and _always_ true) return type that was
previously used. This is not a breaking change, as the docs and
the return type of the main Mockttp interface itself are all
specified as void already.

src/client/mockttp-client.ts

@@ -401,10 +401,10 @@ export class MockttpClient extends AbstractMockttp implements Mockttp {
         throw new Error("Client-side debug info not implemented.");
     }
 
-    reset = async (): Promise<boolean> => {
-        return (await this.queryMockServer<boolean>(
+    reset = async (): Promise<void> => {
+        return (await this.queryMockServer<void>(
             `mutation Reset {
-                    reset
+                reset
             }`
         ));
     }

src/standalone/schema.gql

@@ -14,7 +14,7 @@ type Mutation {
     addWebSocketRules(input: [WebSocketMockRule!]!): [MockedEndpoint!]!
     setWebSocketRules(input: [WebSocketMockRule!]!): [MockedEndpoint!]!
 
-    reset: Boolean!
+    reset: Void
 }
 
 type Subscription {
@@ -121,6 +121,7 @@ type Response {
 }
 
 scalar Any
+scalar Void
 scalar Json
 scalar Buffer
 scalar RequestMatcher

src/standalone/standalone-model.ts

@@ -141,6 +141,14 @@ const ScalarResolvers = {
         parseLiteral: parseAnyAst
     }),
 
+    Void: new GraphQLScalarType({
+        name: 'Void',
+        description: 'Nothing at all',
+        serialize: (value: any) => null,
+        parseValue: (input: string): any => null,
+        parseLiteral: (): any => { throw new Error('Void literals are not supported') }
+    }),
+
     Buffer: new GraphQLScalarType({
         name: 'Buffer',
         description: 'A buffer',
@@ -246,10 +254,7 @@ export function buildStandaloneModel(mockServer: MockttpServer, stream: Duplex):
                 ));
             },
 
-            reset: () => {
-                mockServer.reset();
-                return true;
-            }
+            reset: () => mockServer.reset()
         },
 
         Subscription: {