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

server/auth/delegation_test.go

Index: server/auth/delegation_test.go
diff --git a/server/auth/delegation_test.go b/server/auth/delegation_test.go
index 68fe0553443a5b35f237ed7d9ac7bc3aad5b5e57..413fc650a223930c10e95bb9690061e2aa01273a 100644
--- a/server/auth/delegation_test.go
+++ b/server/auth/delegation_test.go
@@ -38,10 +38,6 @@ type tokenMinterMock struct {
 	err      error
 }
 
-func (m *tokenMinterMock) MintMachineToken(context.Context, *minter.MintMachineTokenRequest, ...grpc.CallOption) (*minter.MintMachineTokenResponse, error) {
-	panic("not implemented")
-}
-
 func (m *tokenMinterMock) MintDelegationToken(ctx context.Context, in *minter.MintDelegationTokenRequest, opts ...grpc.CallOption) (*minter.MintDelegationTokenResponse, error) {
 	m.request = *in
 	if m.err != nil {