token-server: Add protos for new API for generating service account tokens.

tokenserver/client/tokenclient.go

 // Copyright 2016 The LUCI Authors.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //      http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 19 matching lines @@
 
         "github.com/luci/luci-go/tokenserver/api/minter/v1"
 )
 
 // Client can make signed requests to the token server.
 type Client struct {
         // Client is interface to use for raw RPC calls to the token server.
         //
         // Use minter.NewTokenMinterClient (or NewTokenMinterPRPCClient) to
         // create it. Note that transport-level authentication is not needed.
-        Client minter.TokenMinterClient
+        Client TokenMinterClient
 
         // Signer knows how to sign requests using some private key.
         Signer Signer
 }
 
+// TokenMinterClient is subset of minter.TokenMinterClient this package uses.
+type TokenMinterClient interface {
+        // MintMachineToken generates a new token for an authenticated machine.
+        MintMachineToken(context.Context, *minter.MintMachineTokenRequest, ...grpc.CallOption) (*minter.MintMachineTokenResponse, error)
+}
+
 // Signer knows how to sign requests using some private key.
 type Signer interface {
         // Algo returns an algorithm that the signer implements.
         Algo(ctx context.Context) (x509.SignatureAlgorithm, error)
 
         // Certificate returns ASN.1 DER blob with the certificate of the signer.
         Certificate(ctx context.Context) ([]byte, error)
 
         // Sign signs a blob using the private key.
         Sign(ctx context.Context, blob []byte) ([]byte, error)
@@ skipping 88 matching lines @@
                 }
         }
 
         // Must not happen. But better return an error than nil-panic if it does.
         if resp.TokenResponse == nil {
                 return nil, fmt.Errorf("token server didn't return a token")
         }
 
         return resp.TokenResponse, nil
 }