Allow override of discovery URL via ConfigMap

Signed-off-by: Andrew Keesler <akeesler@vmware.com>

- Seems like the next step is to allow override of the CA bundle; I didn't
  do that here for simplicity of the commit, but seems like it is the right
  thing to do in the future.

pkg/config/api/types.go

@@ -7,7 +7,8 @@ package api
 
 // Config contains knobs to setup an instance of placeholder-name.
 type Config struct {
-	WebhookConfig WebhookConfigSpec `json:"webhook"`
+	WebhookConfig   WebhookConfigSpec   `json:"webhook"`
+	DiscoveryConfig DiscoveryConfigSpec `json:"discovery"`
 }
 
 // WebhookConfig contains configuration knobs specific to placeholder-name's use
@@ -21,3 +22,12 @@ type WebhookConfigSpec struct {
 	// to validate TLS connections to the WebhookURL.
 	CABundle []byte `json:"caBundle"`
 }
+
+// DiscoveryConfigSpec contains configuration knobs specific to
+// placeholder-name's publishing of discovery information. These values can be
+// viewed as overrides, i.e., if these are set, then placeholder-name will
+// publish these values in its discovery document instead of the ones it finds.
+type DiscoveryConfigSpec struct {
+	// URL contains the URL at which placeholder-name can be contacted.
+	URL *string `json:"url,omitempty"`
+}

pkg/config/config_test.go

@@ -14,14 +14,50 @@ import (
 )
 
 func TestFromPath(t *testing.T) {
-	expect := require.New(t)
-
-	config, err := FromPath("testdata/happy.yaml")
-	expect.NoError(err)
-	expect.Equal(config, &api.Config{
-		WebhookConfig: api.WebhookConfigSpec{
-			URL:      "https://tuna.com/fish?marlin",
-			CABundle: []byte("-----BEGIN CERTIFICATE-----..."),
+	tests := []struct {
+		name       string
+		path       string
+		wantConfig *api.Config
+	}{
+		{
+			name: "Happy",
+			path: "testdata/happy.yaml",
+			wantConfig: &api.Config{
+				DiscoveryConfig: api.DiscoveryConfigSpec{
+					URL: stringPtr("https://some.discovery/url"),
+				},
+				WebhookConfig: api.WebhookConfigSpec{
+					URL:      "https://tuna.com/fish?marlin",
+					CABundle: []byte("-----BEGIN CERTIFICATE-----..."),
+				},
+			},
 		},
-	})
+		{
+			name: "NoDiscovery",
+			path: "testdata/no-discovery.yaml",
+			wantConfig: &api.Config{
+				DiscoveryConfig: api.DiscoveryConfigSpec{
+					URL: nil,
+				},
+				WebhookConfig: api.WebhookConfigSpec{
+					URL:      "https://tuna.com/fish?marlin",
+					CABundle: []byte("-----BEGIN CERTIFICATE-----..."),
+				},
+			},
+		},
+	}
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			config, err := FromPath(test.path)
+			require.NoError(t, err)
+			require.Equal(t, test.wantConfig, config)
+		})
+	}
+}
+
+func stringPtr(s string) *string {
+	sPtr := new(string)
+	*sPtr = s
+	return sPtr
 }

pkg/config/testdata/happy.yaml

@@ -1,4 +1,6 @@
 ---
+discovery:
+  url: https://some.discovery/url
 webhook:
   url: https://tuna.com/fish?marlin
   caBundle: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tLi4u

pkg/config/testdata/no-discovery.yaml

@@ -0,0 +1,5 @@
+---
+webhook:
+  url: https://tuna.com/fish?marlin
+  caBundle: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tLi4u
+