Add possibility to add and drop hpke configs

Makefile

@@ -0,0 +1,4 @@
+test:
+	go test ./...
+
+all: test

ohttp.go

@@ -418,6 +418,33 @@ func (g Gateway) Config(keyID uint8) (PublicConfig, error) {
 	return PublicConfig{}, fmt.Errorf("unknown keyID %d", keyID)
 }
 
+func (g *Gateway) DropKeyFromConfig(keyID uint8) error {
+	if _, ok := g.keyMap[keyID]; !ok {
+		return fmt.Errorf("unknown keyID %d", keyID)
+	}
+
+	delete(g.keyMap, keyID)
+
+	newKeys := make([]uint8, 0, len(g.keys)-1)
+	for key := range g.keyMap {
+		newKeys = append(newKeys, key)
+	}
+	g.keys = newKeys
+
+	return nil
+}
+
+func (g *Gateway) AddKeyToConfig(config PrivateConfig) error {
+	if _, exists := g.keyMap[config.publicConfig.ID]; exists {
+		return fmt.Errorf("duplicate config key ID")
+	}
+
+	g.keyMap[config.publicConfig.ID] = config
+	g.keys = append(g.keys, config.publicConfig.ID)
+
+	return nil
+}
+
 func (g Gateway) Client(keyID uint8) (Client, error) {
 	config, err := g.Config(keyID)
 	if err != nil {

ohttp_test.go

@@ -581,3 +581,17 @@ func BenchmarkRoundTrip(b *testing.B) {
 		require.Equal(b, rawResponse, receivedResp, "Response mismatch")
 	})
 }
+
+func TestPopAndAddConfigs(t *testing.T) {
+
+	privateConfig, err := NewConfig(0x00, hpke.KEM_X25519_HKDF_SHA256, hpke.KDF_HKDF_SHA256, hpke.AEAD_AES128GCM)
+	require.Nil(t, err, "CreatePrivateConfig failed")
+
+	server := NewDefaultGateway([]PrivateConfig{privateConfig})
+
+	err = server.DropKeyFromConfig(0x00)
+	require.Nil(t, err, "DropConfig failed")
+
+	err = server.AddKeyToConfig(privateConfig)
+	require.Nil(t, err, "DropConfig failed")
+}