plugin/grpc: New gRPC plugin (#2667)

* plugin/grpc: New gRPC plugin

* some changes after the first review:

- remove healthcheck. gRPC already has this implicitly implemented
- some naming and stetic changes
- fix some comments
- other minor fixes

* plugin/grpc: New gRPC plugin

* some changes after the first review:

- remove healthcheck. gRPC already has this implicitly implemented
- some naming and stetic changes
- fix some comments
- other minor fixes

* add OWNERS file and change plugin order

* remove Rcode checker

plugin/grpc/setup_policy_test.go

@@ -0,0 +1,47 @@
+package grpc
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/mholt/caddy"
+)
+
+func TestSetupPolicy(t *testing.T) {
+	tests := []struct {
+		input          string
+		shouldErr      bool
+		expectedPolicy string
+		expectedErr    string
+	}{
+		// positive
+		{"grpc . 127.0.0.1 {\npolicy random\n}\n", false, "random", ""},
+		{"grpc . 127.0.0.1 {\npolicy round_robin\n}\n", false, "round_robin", ""},
+		{"grpc . 127.0.0.1 {\npolicy sequential\n}\n", false, "sequential", ""},
+		// negative
+		{"grpc . 127.0.0.1 {\npolicy random2\n}\n", true, "random", "unknown policy"},
+	}
+
+	for i, test := range tests {
+		c := caddy.NewTestController("dns", test.input)
+		g, err := parseGRPC(c)
+
+		if test.shouldErr && err == nil {
+			t.Errorf("Test %d: expected error but found %s for input %s", i, err, test.input)
+		}
+
+		if err != nil {
+			if !test.shouldErr {
+				t.Errorf("Test %d: expected no error but found one for input %s, got: %v", i, test.input, err)
+			}
+
+			if !strings.Contains(err.Error(), test.expectedErr) {
+				t.Errorf("Test %d: expected error to contain: %v, found error: %v, input: %s", i, test.expectedErr, err, test.input)
+			}
+		}
+
+		if !test.shouldErr && g.p.String() != test.expectedPolicy {
+			t.Errorf("Test %d: expected: %s, got: %s", i, test.expectedPolicy, g.p.String())
+		}
+	}
+}