[web] add client interceptors for grpc-web

Summary:
these interceptors will be used to add version and auth metadata to our RPCs.

Depends on D9671

Test Plan: https://gist.github.com/vdhanan/15ffc5810425b8a22b7d3c5bd01a8d58

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: bartek, tomek, wyilio

Differential Revision: https://phab.comm.dev/D9672

web/grpc/interceptor.js

@@ -0,0 +1,53 @@
+// @flow
+
+import * as grpcWeb from 'grpc-web';
+
+import { getConfig } from 'lib/utils/config.js';
+
+class VersionInterceptor<Request, Response> {
+  intercept(
+    request: grpcWeb.Request<Request, Response>,
+    invoker: (
+      request: grpcWeb.Request<Request, Response>,
+    ) => Promise<grpcWeb.UnaryResponse<Request, Response>>,
+  ): Promise<grpcWeb.UnaryResponse<Request, Response>> {
+    const metadata = request.getMetadata();
+    const config = getConfig();
+    const codeVersion = config.platformDetails.codeVersion;
+    const deviceType = config.platformDetails.platform;
+    if (codeVersion) {
+      metadata['code_version'] = codeVersion.toString();
+    }
+    metadata['device_type'] = deviceType;
+
+    return invoker(request);
+  }
+}
+
+class AuthInterceptor<Request, Response> {
+  userID: string;
+  deviceID: string;
+  accessToken: string;
+
+  constructor(userID: string, deviceID: string, accessToken: string) {
+    this.userID = userID;
+    this.deviceID = deviceID;
+    this.accessToken = accessToken;
+  }
+
+  intercept(
+    request: grpcWeb.Request<Request, Response>,
+    invoker: (
+      request: grpcWeb.Request<Request, Response>,
+    ) => Promise<grpcWeb.UnaryResponse<Request, Response>>,
+  ): Promise<grpcWeb.UnaryResponse<Request, Response>> {
+    const metadata = request.getMetadata();
+    metadata['user_id'] = this.userID;
+    metadata['device_id'] = this.deviceID;
+    metadata['access_token'] = this.accessToken;
+
+    return invoker(request);
+  }
+}
+
+export { VersionInterceptor, AuthInterceptor };