add final attributes to classes

Plugin/Templates/client-call-bidistreaming.swift

@@ -1,5 +1,5 @@
 /// {{ method|methodDescriptorName }} (Bidirectional Streaming)
-{{ access }} class {{ .|call:file,service,method }} {
+{{ access }} final class {{ .|call:file,service,method }} {
   private var call : Call
 
   /// Create a call.

Plugin/Templates/client-call-clientstreaming.swift

@@ -1,5 +1,5 @@
 /// {{ method|methodDescriptorName }} (Client Streaming)
-{{ access }} class {{ .|call:file,service,method }} {
+{{ access }} final class {{ .|call:file,service,method }} {
   private var call : Call
 
   /// Create a call.

Plugin/Templates/client-call-serverstreaming.swift

@@ -1,5 +1,5 @@
 /// {{ method|methodDescriptorName }} (Server Streaming)
-{{ access }} class {{ .|call:file,service,method }} {
+{{ access }} final class {{ .|call:file,service,method }} {
   private var call : Call
 
   /// Create a call.

Plugin/Templates/client-call-unary.swift

@@ -1,5 +1,5 @@
 /// {{ method|methodDescriptorName }} (Unary)
-{{ access }} class {{ .|call:file,service,method }} {
+{{ access }} final class {{ .|call:file,service,method }} {
   private var call : Call
 
   /// Create a call.

Plugin/Templates/client.swift

@@ -22,7 +22,7 @@
 //-{% endif %}
 //-{% endfor %}
 /// Call methods of this class to make API calls.
-{{ access }} class {{ .|serviceclass:file,service }} {
+{{ access }} final class {{ .|serviceclass:file,service }} {
   public var channel: Channel
 
   /// This metadata will be sent with all requests.

Plugin/Templates/server-session-bidistreaming.swift

@@ -1,5 +1,5 @@
 // {{ method|methodDescriptorName }} (Bidirectional Streaming)
-{{ access }} class {{ .|session:file,service,method }} : {{ .|service:file,service }}Session {
+{{ access }} final class {{ .|session:file,service,method }} : {{ .|service:file,service }}Session {
   private var provider : {{ .|provider:file,service }}
 
   /// Create a session.

Plugin/Templates/server-session-clientstreaming.swift

@@ -1,5 +1,5 @@
 // {{ method|methodDescriptorName }} (Client Streaming)
-{{ access }} class {{ .|session:file,service,method }} : {{ .|service:file,service }}Session {
+{{ access }} final class {{ .|session:file,service,method }} : {{ .|service:file,service }}Session {
   private var provider : {{ .|provider:file,service }}
 
   /// Create a session.

Plugin/Templates/server-session-serverstreaming.swift

@@ -1,5 +1,5 @@
 // {{ method|methodDescriptorName }} (Server Streaming)
-{{ access }} class {{ .|session:file,service,method }} : {{ .|service:file,service }}Session {
+{{ access }} final class {{ .|session:file,service,method }} : {{ .|service:file,service }}Session {
   private var provider : {{ .|provider:file,service }}
 
   /// Create a session.

Plugin/Templates/server-session-unary.swift

@@ -1,5 +1,5 @@
 // {{ method|methodDescriptorName }} (Unary)
-{{ access }} class {{ .|session:file,service,method }} : {{ .|service:file,service }}Session {
+{{ access }} final class {{ .|session:file,service,method }} : {{ .|service:file,service }}Session {
   private var provider : {{ .|provider:file,service }}
 
   /// Create a session.

Plugin/Templates/server.swift

@@ -24,7 +24,7 @@
 }
 
 /// Common properties available in each service session.
-{{ access }} class {{ .|service:file,service }}Session {
+{{ access }} final class {{ .|service:file,service }}Session {
   fileprivate var handler : gRPC.Handler
   {{ access }} var requestMetadata : Metadata { return handler.requestMetadata }
 
@@ -54,7 +54,7 @@
 //-{% endfor %}
 
 /// Main server for generated service
-{{ access }} class {{ .|server:file,service }} {
+{{ access }} final class {{ .|server:file,service }} {
   private var address: String
   private var server: gRPC.Server
   private var provider: {{ .|provider:file,service }}?