docs/grpc: add macaroon and SSL Cipher info to Ruby gRPC docs

docs/grpc/ruby.md

@@ -42,7 +42,9 @@ Two files will be generated in the current directory:
 * `rpc_pb.rb`
 * `rpc_services_pb.rb`
 
-### Example - Simple client to display wallet balance
+### Examples
+
+#### Simple client to display wallet balance
 
 Every time you use the Ruby gRPC you need to require the `rpc_services_pb` file.
 
@@ -58,6 +60,11 @@ $:.unshift(File.dirname(__FILE__))
 require 'grpc'
 require 'rpc_services_pb'
 
+# Due to updated ECDSA generated tls.cert we need to let gprc know that
+# we need to use that cipher suite otherwise there will be a handhsake
+# error when we communicate with the lnd rpc server.
+ENV['GRPC_SSL_CIPHER_SUITES'] = "HIGH+ECDSA"
+
 certificate = File.read(File.expand_path("~/.lnd/tls.cert"))
 credentials = GRPC::Core::ChannelCredentials.new(certificate)
 stub = Lnrpc::Lightning::Stub.new('127.0.0.1:10009', credentials)
@@ -68,7 +75,7 @@ puts "Total balance: #{response.total_balance}"
 
 This will show the `total_balance` of the wallet.
 
-#### Example - Streaming client for invoice payment updates
+#### Streaming client for invoice payment updates
 
 ```ruby
 #!/usr/bin/env ruby
@@ -78,6 +85,8 @@ $:.unshift(File.dirname(__FILE__))
 require 'grpc'
 require 'rpc_services_pb'
 
+ENV['GRPC_SSL_CIPHER_SUITES'] = "HIGH+ECDSA"
+
 certificate = File.read(File.expand_path("~/.lnd/tls.cert"))
 credentials = GRPC::Core::ChannelCredentials.new(certificate)
 stub = Lnrpc::Lightning::Stub.new('127.0.0.1:10009', credentials)
@@ -104,3 +113,56 @@ $ lncli sendpayment --pay_req=<PAY_REQ>
 ```
 
 You should now see the details of the settled invoice appear.
+
+#### Using Macaroons
+
+To authenticate using macaroons you need to include the macaroon in the metadata of the request.
+
+```ruby
+# Lnd admin macaroon is at ~/.lnd/admin.macaroon on Linux and
+# ~/Library/Application Support/Lnd/admin.macaroon on Mac
+macaroon_binary = File.read(File.expand_path("~/.lnd/admin.macaroon"))
+macaroon = macaroon_binary.each_byte.map { |b| b.to_s(16).rjust(2,'0') }.join
+```
+
+The simplest approach to use the macaroon is to include the metadata in each request as shown below.
+
+```ruby
+stub.get_info(Lnrpc::GetInfoRequest.new, metadata: {metadata: macaroon})
+```
+
+However, this can get tiresome to do for each request. We can use gRPC interceptors to add this metadata to each request automatically. Our interceptor class would look like this.
+
+```ruby
+class MacaroonInterceptor < GRPC::ClientInterceptor
+  attr_reader :macaroon
+
+  def initialize(macaroon)
+    @macaroon = macaroon
+    super
+  end
+
+  def request_response(request:, call:, method:, metadata:)
+    metadata['macaroon'] = macaroon
+    yield
+  end
+end
+```
+
+And then we would include it when we create our stub like so.
+
+```ruby
+certificate = File.read(File.expand_path("~/.lnd/tls.cert"))
+credentials = GRPC::Core::ChannelCredentials.new(certificate)
+macaroon_binary = File.read(File.expand_path("~/.lnd/admin.macaroon"))
+macaroon = macaroon_binary.each_byte.map { |b| b.to_s(16).rjust(2,'0') }.join
+
+stub = Lnrpc::Lightning::Stub.new(
+	'localhost:10009',
+	credentials,
+	interceptors: [MacaroonInterceptor.new(macaroon)]
+)
+
+# Now we don't need to pass the metadata on a request level
+p stub.get_info(Lnrpc::GetInfoRequest.new)
+```